Bienstock has shown that the growth of Bac. putrificus is inhibited by the action of Bact. coli commune, which is capable of setting up a slight lactic acid fermentation. Bact. coli commune, however, gives rise to substances of an injurious character, and, although present very abundantly in the intestinal tract, it may by reduced almost entirely by the active growth of lactic acid bacteria. This fact is of great value to the cheese-maker, since by the addition of a lactic acid culture (starter) to milk before renneting, gas-producing bacteria such as Bact. coli may be checked in growth. Since the ordinary lactic acid bacteria such as Streptococcus lacticus, Bac. lactis acidi, and others, are incapable of growth at blood temperature, it appeared necessary to procure cultures of lactic bacteria able to grow at temperatures of 100° F. to 112° F. Such an organism was found in Bulgarian soured milk (yoghourt), and was considered pre-eminently adapted to this purpose. As has been shown in the preceding paragraphs, this organism is merely one of a large group of bacteria found distributed in the intestinal canal of many domestic animals, in manure, and in ordinary market milk. It is then not surprising that the introduction into the intestinal tract of bacteria of the type Bulgaricus in the form of tabloids has not met with any decided success. Although it was considered to be merely necessary to introduce the desired type of organism into the body, and the amount of lactic acid taken into the system by the administration of soured milks was looked upon as of secondary importance, yet, it would seem, in the light of recent investigations, that benefits derived from a soured milk regimen are attributable in part to a chemical as well as a purely bacterial action. This receives support from the fact that soured milk beverages prepared by the use of ordinary lactic bacteria, distinct from those of the Bulgaricus type, often exert a beneficial influence upon human beings even although the organisms responsible for the fermentation are incapable of growth at blood temperature.

It may be mentioned in conclusion that cultures prepared by the use of organisms of the type Streptococcus lacticus combined with Bac. bulgaricus possess a more agreeable flavour and aroma than those prepared from a pure culture of Bulgaricus alone.

CHAPTER VI

THE PREPARATION OF SOURED MILK IN THE HOUSE

There is no great difficulty in making soured milk at home: the necessary operations are quite simple, but at the same time they must be conducted with precision and care, otherwise the results may be unsatisfactory and disagreeable; there may even sometimes be danger in badly prepared sour milk. It is always an advantage in such matters to understand the reason of things, and a few notes on the surrounding conditions, and what has to be accomplished, may be of assistance to the would-be experimenter.

The majority of intelligent people are now acquainted with the fact that the germs of bacteria are to be found everywhere on the surface of the earth, in air, and in water, and that they are the sole cause of the decay of all manner of perishable articles.

The distribution is unequal—bacteria are much more plentiful where there is decaying matter—in dirty houses, sewage, or other contaminated water, etc. Milk is a splendid food for bacteria, and numerous varieties multiply in it exceedingly, and many of these are injurious, producing putrefactive changes which render the milk unwholesome, even poisonous in some cases. Others are beneficial, and are absolutely necessary for the souring of milk for making butter or cheese and for the ripening of the latter. The soured milk which is the subject of this book is the work of certain lactic-acid-producing bacteria, and the problem we have before us is to encourage the growth of the latter to the uttermost and to exclude the others.

As bacterial germs are present in the air and readily sow themselves into any medium with which they come in contact, the first consideration is to get good fresh milk which has been as little exposed to the air as possible. The second is to conduct the experiment where the germs are fewest, and in cleanly surroundings, far removed from decaying matter and free from taints and smells.

However fresh the milk may be, it will contain useless or injurious bacteria, and we must get rid of these before attempting to introduce those whose growth we wish to encourage. This is effected by heat. All the living bacteria and most of the germs are killed at temperatures somewhat under the boiling point. Having sterilised the milk in this way, it is necessary, as far as possible, to prevent the entrance of fresh germs from the atmosphere, and we therefore let the milk cool down in covered dishes. When the temperature descends to about 100° F. the culture of the special bacteria is introduced, the covers are replaced, and the milk vessels maintained at or near this temperature for twelve hours, when the soured milk is ready for use. It is not necessary to use fresh culture every time—a little of the soured milk will take its place, and this may be repeated as many as fourteen times before it is necessary to start off again with a fresh culture. A great deal depends on the care exercised and the freedom of the surroundings from bacterial germs. Under the best conditions wild germs will gradually accumulate in the soured milk, but their increase may be greatly delayed by attention to the precautions mentioned. The ordinary souring of milk for butter and cheese making is conducted in cool surroundings, as already stated, because in such conditions the lactic-acid-producing germs increase relatively faster than the wild germs, and so gain the upper hand, but in the case of our special soured milk we kill out, practically, all wild bacteria and germs, and the pure culture having the field to itself, we can conduct the operation at a higher temperature where the action of the bacteria is at its maximum, and so obtain the necessary lactification in the minimum of time.

The appliances for the souring of milk on the domestic scale require some consideration. We propose to describe the principal forms of apparatus which have been put on the market for the purpose, and then to give such suggestions as may assist the ingenious in making apparatus for themselves. Those who wish for information on the subject of larger apparatus will find it in the following chapter.

The Society "Le Ferment" of Paris, which has been authorised by Professor Metchnikoff to prepare and supply to the public his sour milk culture, provides an apparatus for the treatment of the milk. It is shown in Fig. 45, which consists of a double box having the intervening space packed with a non-conducting material. It is provided with a tight lid. Inside, there is accommodation for two milk vessels, each with a capacity of about two thirds of a pint. The most difficult thing in the souring of milk is to maintain the temperature as nearly at 100° F. as possible while the culture is in action. This result is attained by filling the vessel in the middle with boiling water. The insulated walls hinder the escape of heat, and the quantity of boiling water used is calculated to maintain the temperature steady for the twelve hours of cultivation; but in cold, frosty weather it is necessary to refill the central vessel with boiling water in the middle of the period.

The milk jars are washed with hot boiled water and turned upside down to dry. They should not be wiped with a cloth. Boil the milk to be treated for ten minutes, stirring it to promote evaporation, as it is advantageous to have it in concentrated form. Cool rapidly to 100° F. by placing the boiling vessel in cold water, add to each bowl one third of a tube of the culture in powder form, fill up with the boiled and cooled milk, stir well and cover. Place the jars in the box and fill the central vessel with boiling water, shut the lid tight, and do not open it (unless a fresh charge of boiling water is needed) for ten or twelve hours, when it will be ready for use. If the liquid culture is used (one small phial for each bowl) the milk should be cooled to 86° F. instead of 100° F., as with the powder. The culture is also supplied in tabloid form. The powder and tabloids keep well, but the liquid can only be relied on for about two months. The milk prepared as above should be stored in a cool place, the lids being kept on the bowls. It is good for about two days, after which it becomes too sour. It can be eaten with sugar, which not only sweetens it but is beneficial in affording additional suitable food for the acid-producing bacilli. If fresh milk cannot be had, condensed, sterilised, or pasteurised milk may be used, but, of course, fresh milk is best. Condensed milk should be diluted with two parts of boiling water and then treated like ordinary milk.

An apparatus on similar principles is sold by the Maya Bulgare Company, Ltd., and is illustrated in Fig. 46.

Lactic Ferments, Limited, make use of a different principle to maintain the temperature steady during the lactifying period. Their apparatus (Fig. 47) consists Soured Milk Apparatus of the Maya Bulgare Company, Limited Fig. 47 of a water vessel mounted on a stand. The milk vessels (tumblers) are placed in the water, and the temperature maintained at the proper figure by a small night light burning underneath. It is recommended that the milk should be placed in an earthenware jar or jug, which is stood in a pot of water kept boiling for an hour. After cooling add from three to six previously crushed tabloids of culture, and stir well with a glass rod which has been sterilised in boiling water. The milk is then transferred to three tumblers, which it should fill, and these are put into the water vessel, the water in which should be at about 100° F., and the night light started.

Messrs. Allen & Hanbury, Limited, also make use of the night light to maintain the proper temperature during incubation in their "Sauerin" apparatus (Fig. 48).

No water, however, is placed in the metal container. The procedure is the same as that already described, and both tablet and liquid pure cultures are supplied. For children it is recommended that the incubation should occupy from three to four hours only, in other cases eight to ten hours. Grated nutmeg, ground cinnamon, or other flavouring, and cream may be used with the soured milk.

The night light is also employed in the "Veronelle" apparatus of Messrs. Clay, Paget and Company, Limited (Fig. 49).

The containing vessel is of tin or aluminium, and has two stands, the high one for hot and the low one for cold weather, as in the latter case greater heat is needed to maintain the incubating temperature. The milk is placed in an earthenware jar and is sterilised by placing it in a saucepan of water and boiling it; continuing the boiling for half an hour. It is allowed to cool to about 98° F., and placed in the incubator, culture added, and the lamp lighted, the cover of the incubator being kept on. The period of incubation is given as six hours. To prepare the next day's supply a tablespoonful of the soured milk is retained and used instead of the culture. This may be continued for fourteen days, when a fresh start with culture is necessary. The soured milk will keep for thirty-six hours. Capacity, one and one half and two pints; also a large size for family use.

For the preparation of soured milk on a small scale, one of the various forms of vacuum flasks now on the market may be used with satisfactory results. A little cold water must be poured into the flasks, and warm water added, until, by means of three to four changes, boiling water can be safely poured in without cracking the flask.

This boiling water must be allowed to remain in for about twenty minutes, and then replaced by freshly boiled milk that has been cooled, so that its temperature in the flask is about 105° F. The culture of lactic organisms should then be added, the opening of the flask plugged with clean cotton-wool, and the cap screwed on.

In an actual test, the temperature of the milk placed in such a flask was 105° F., at 7.30 P.M., and had dropped to 93° F. by 9 A.M., the following day. The milk was curdled, and possessed the normal acid taste of such cultures.

The different types of apparatus are all quite simple, and it would be easy to make something at home. Get two round tins, the one less in diameter by from two to three inches than the other, put one or two pieces of wood across the bottom inside the larger tin, and fill up the space between with cotton-wool, which is an excellent non-conductor of heat. Place the smaller tin centrally inside the larger one. Fix three or four distance pieces of wood in the space between them, fill up with cotton-wool, leaving a little space at the top to permit the lid of the smaller tin to be fixed on. The boiling-water vessel may be a tin saucepan with a lid, but no handle, and its proper place would be on the bottom of the inner tin. A tripod stand made of three pieces of wire bound together, and with legs reaching past the hot-water vessel to the bottom of the tin, would support a false bottom of tin forming the shelf on which the vessels of milk to be treated would rest. These might be tumblers covered with tin lids. To prevent radiation through the lid of the inner tin, a thick pad or hood of cotton-wool packed between cloth would be placed over the top. A little experimenting would be necessary to determine the quantity of boiling water required to maintain the proper temperature.

The soured milk obtained in the above manner is of the consistency of ordinary buttermilk; a separation of whey frequently takes place, and this may be poured off if desired. The taste and flavour should be pleasantly acid and agreeable, and both are distinctive enough to give a good idea of the purity of the product. In many places a more concentrated article is made by boiling down the milk to one half or one third of its bulk, and then fermenting it in the ordinary way. A kind of thick pudding is thus obtained, which is highly recommended both as an agreeable article of food and as a stronger medium for the support of the germs it is the purpose of the sour milk treatment to introduce into the digestive system.

The cultures for making soured milk can now be had from all the leading wholesale and retail chemists, with directions as to the quantities to be used.

It is very necessary that the milk used should be not only fresh and good, but also free from chemical preservatives. The effect of these is to inhibit the growth and development of bacteria, and they have therefore an injurious influence on the special lactifying germs it is our object to cultivate. Preservatives are now not nearly so much used as they were, a few years ago, and there should be no difficulty in obtaining milk free from them.

For keeping both fresh and soured milk good a small ice-chest is an excellent device. The germs which are continually dropping into milk kept in open vessels in the air, even in cleanly surroundings, are mostly kept out in the close ice-chest, and the low temperature prevents in a natural way the development of the bacterial germs already in the milk. For the preservation of all kinds of foods the ice-chest is a capital investment, not to mention the benefit of having cooled drinks, etc., as required. They manage things well in this respect in the United States, where ice is regarded as a necessity in the summer time by even the poorest people, and is delivered with the same regularity as the milk.

It is necessary to utter a word of warning as to certain forms in which the sour milk bacillus is being offered to the public. It is being compounded with sugar, chocolate, and other articles, and sold in the form of sweets, etc. There is no reliable proof that these preparations are valuable. Certainly, sugar is a medium in which the lactifying germs can live, but the quantity so introduced into the system must be very small compared with what is obtained from properly fermented milk. It takes some time, even with strong cultures, to fix the acid-producing germs in the large bowel where they are wanted, and until proper evidence is forthcoming that confectionery preparations are efficacious we would recommend that only the regularly fermented milk be used. It would save trouble, no doubt, to treat oneself with a few chocolate creams containing the necessary germs daily, but if the matter is taken up seriously it will be better to take some pains and stick to methods the efficacy of which has been demonstrated, leaving the others until their bona fides has been proved. There are always enterprising firms who are prepared to simplify things for us, but we must make sure that their simplifications are warranted.

CHAPTER VII

THE PREPARATION OF SOURED MILK IN THE DAIRY

There is a tendency in certain medical quarters to discourage the use of soured milk "made for profit." This view leaves out of account the fact that besides being of value in medicine, the article in question is also an excellent food, which, as we have seen, has been consumed by multitudes of people for ages in many parts of the world. There seems also to be satisfactory evidence that a larger percentage than usual of the people who make soured milk a staple of diet attain to a ripe old age. How does it become such a dangerous thing the moment the doctors get it into their hands? Of course if a man has an acute disease he places himself entirely in the hands of his medical man, and eats what is prescribed for him, or at least he ought to do so, and if he makes such a submission he is entitled at least to the comfort of being able to feel that his doctor is free from unreasonable prejudices. For the implication that an article "made for profit" is naturally suspect casts an unwarranted stigma on a large number of honourable people. There are dishonest tradesmen just as there are dishonest and careless doctors, but to saddle a whole class with the offences of a few would not be a justifiable proceeding in either case. Besides, it is not to the interest of the manufacturing chemist or the dairyman to turn out spurious cultures or bad soured milk, and on the whole we see no reason why they should not engage in the business.

The widespread use of soured milk in other countries as a regular article of diet seems to indicate that all manner of people, except those suffering from diseases which necessitate medical regulation of diet, might with probable benefit to themselves add this article to their food list; and it looks as if a good many of them intend doing so, even if scandalised doctors threaten "to abandon the cure."

The dairyman who knows his business does not need to be told of the care which is necessary to keep milk in good condition. The merely commercial consideration of avoiding loss has made him ready to inquire into the best means of prolonging the life of milk as a merchantable article. For a time he relied on chemical preservatives, but their day is now almost over, and filtration, pasteurisation, and cold storage have taken their place. Any one conversant with the trade knows how widely these methods have been adopted of late years; we may, therefore, assume that the average dairyman has at his command milk suitable for the incubation process.

The demand for soured milk is not as yet a very large one, and the apparatus so far developed for its production is meant for the treatment of small quantities. After describing the principal appliances at present in the market we propose to make some suggestions as to the construction of larger apparatus.

A firm which has given great attention to the question of maintaining fixed temperatures is that of Messrs. Charles Hearson & Co., Ltd. Their incubators for chicken hatching are known all over the world; and their appliances for biological incubation are very generally used in bacteriological laboratories. With such experience it was natural that they should turn their attention to soured milk apparatus, and the result is the "Lactobator" (Figs. 50 and 51).

A copper vessel made to contain water has placed in it a stoneware jar which holds two gallons of milk; on the top is a lid which carries a thermometer for indicating the temperature of the milk. Heat is supplied by a gas ring under the copper vessel; and in the gas supply is the patent thermostat made use of by Messrs. Hearson also in their biological and poultry incubators, in which a capsule containing a liquid arranged to boil at a certain predetermined temperature is the regulating factor. When the liquid boils, the capsule expands, and by certain mechanical devices regulates the gas supply so as to produce exactly the temperature required.

The procedure is as follows: The jar is filled with milk, and water is run into the copper vessel by the funnel until it runs over at the overflow pipe. The thermostat is lifted off and the full gas supply allowed to pass to the burner, the temperature of the milk brought up to 180° F. and maintained for half an hour at this figure. The gas is then turned off, and cold water run through the funnel until the temperature of the milk registers 95° F. The culture is added, the lid replaced, and the thermostat put into the pocket at the side of the vessel; the gas relighted, and when the temperature reaches 100° to 106° F. the capsule of the thermostat will expand and close the gas to a peep, which is just sufficient to maintain the temperature within the above limits. After eight hours the incubation is completed.

Edgar's patent apparatus, the "Lactogenerator," as provided by the Dairy Supply Co., Ltd., is shown in Fig. 52.

The milk is placed in a tinned copper-jacketed vessel and water run in through a vertical pipe until it runs off at the overflow. Two gas connections are required with cocks on each, the one to heat up the milk to the boiling point and maintain it at this for thirty minutes. A skimmer which has been placed in the milk lifts out the coagulated protein and albumen which rise to the top. The cock is then shut and cold water run through the jacket till the thermometer shows 90° F., when the culture is added, and the other gas supply with the regulator turned on, and the temperature is automatically maintained at about 90° F. Time of incubation eight to nine hours. It is recommended to turn cold water into the jacket at the end of the period to prevent overincubation.

A somewhat similar apparatus is that of the Willows Refrigerating Co., Ltd. (Fig. 53), with the exception that it has no automatic heat regulator. It is made of tinned steel, and the operations are the same, but the sterilising temperature (obtained by a gas ring or hot plate) is given as 180°, and the incubating temperature 100° to 104° F. for a period of twelve hours. Presumably this temperature is maintained by a small gas jet or other similar source of heat. The capacity is two gallons.

In the apparatus hitherto described the milk is sterilised in bulk, and is filled into bottles or jars after incubation, which is not a desirable thing to do, unless the soured milk is for immediate consumption, as there is likely to be contamination with injurious germs from the atmosphere. In the domestic apparatus the milk is usually incubated in covered jars in which it can be kept until required for use, and the practice on the larger scale should be the same.

The Dairy Outfit Co., Ltd., have recognised this in their "Lacto" apparatus (Fig. 54).

A cylindrical vessel is set loosely on a stand, beneath which is a lamp calculated to maintain the incubating temperature. The milk is placed in bottles with metal screw tops, and these are put into the cylindrical vessel; water is run in round them through the side funnel, the vessel lifted off the stand, and heated to sterilising point on a stove. Cold water is then run in through the funnel until the temperature is low enough for incubation. Culture is added to each bottle and the lids screwed on, the vessel lifted on to its stand, and the lamp lighted. The cover of the apparatus has a thermometer fixed on it.

On the large scale the treatment of the milk would take place entirely in the jars in which it would be sent out, and the sterilisation and incubation would be conducted in different pieces of apparatus. The sterilisation would be effected either (1) by direct steaming, or (2) by hot water heated by steam. Fig. 55 shows the first type of sterilisation. The tank is of wrought iron or steel with strengthening pieces of angle iron. The door, with pulleys and counterweight for easy handling, is fastened steam-tight by hinged bolts. The apparatus is mounted on a stand at a convenient height for handling the bottles; and in front is another stand with channel iron rails to take the waggon in which the bottles or jars to be sterilised are packed. When the door is fast, steam is turned on, and regulated to produce the proper temperature by the thermometer fixed in the shell, in which a pressure gauge is also secured. After sterilising, the door is opened and the waggon drawn forward to the outside, allowed to cool, or removed elsewhere to cool, and allow space for a new charge.

Incubation in bottles or jars, sterilised in these ways, can best be conducted in an insulated room, with say, six inches of silicate cotton, granulated cork, or washed cow hair packed between two-inch by six-inch battens, covered with matching on either side, and lined with sheet zinc. It would be an advantage to have an air-lock or anteroom into which the waggons or trays of sterilised jars could be run, and the door of the anteroom closed before the door of the insulated room is opened. This would tend to prevent variations of temperature in the room, and also, by checking free communication with the outside air, decrease contamination. The waggons of jars would be run in, and culture added to each jar by a sterilised pipette. The atmosphere of the room would be kept pure by running in air frequently through a filter of moist cotton-wool by means of an electric fan, and at intervals the interior would be sterilised by the use of formalin vapour.

Details of an American Apparatus for Preparing Soured Milk

The incubating temperature could very conveniently be maintained by an electric radiator, and as the insulation would largely prevent leakage, the amount of electric current used would not be large. The regulating apparatus might consist of a thermometer with platinum wires fused through the stem at the proper temperature, say 100° F. When the mercury rises to this figure it will complete the circuit of a battery which will actuate certain well-known devices for turning off the current which actuates the radiator. In this way a very fine automatic arrangement would be achieved. Steam pipes might be used instead of the radiator, and the thermometer above described could be used in this case also, with appliances to cut off the steam.

On the large scale, labour-saving appliances, such as the mechanical brush jar and bottle washer, and the automatic filler for jars or bottles, would be employed, and an overhead trackway for carrying the trays of jars from the steriliser to the incubator would be a great convenience. A further adjunct of considerable importance would be a cold room, worked either by ice or a refrigerating machine, in which the jars could be stored after incubation, so as to arrest the process of lactification, and maintain the soured milk in good condition until required for use.

CHAPTER VIII

SOURED MILK IN HEALTH AND DISEASE

When people are ill the best thing they can do is to place themselves in the hands of the doctor, who will try to regulate their lives, including their diet, in accordance with the conditions which science suggests as the most likely to lead to their recovery.

It is not the aim of this book to teach persons who should be under medical treatment to doctor themselves; soured milk may or may not be beneficial in their case—that is for the medical man to say; and further, if it should be beneficial the doctor ought to have its preparation under his control. Slight differences in quality and purity may count for much in cases of acute disease, differences which might not matter to the person who requires no medical attention, and who consumes the article as a health-giving food. A considerable body of evidence is already on record as to the potency in certain cases of soured milk as a curative agent, and it seems to have taken its place in medicine as a recognised remedy.

There is a wide field of usefulness, however, outside of the strictly medical one. Professor Metchnikoff has collected many striking examples of individuals and peoples inhabiting different parts of the world, who thrive, and in many cases attain to a great age, and whose diet consists largely of soured milk. He has made a wide and general inquiry into the causes which tend to shorten life, and makes out a strong case in support of the view that in many cases this is the result of what is called auto-intoxication or self-poisoning. In man and in the mammalia generally, the colon or large intestine is very largely developed; this organ is not of much value in the digestion of food, and seems to be chiefly a receptacle for waste material; it is, as a rule, extremely rich in bacterial flora, which produce putrefactive changes in the waste material. As a result various poisonous principles are evolved, and these find their way into the blood, accompanied frequently, there is every reason to believe, by the injurious bacteria themselves. In this way many diseases and ailments are produced which shorten life. The inquiry then naturally turns to what is the best way of dealing with this state of matters. It is known that the bacteria referred to flourish best in alkaline or at least non-acid surroundings, and it is known that these conditions very frequently exist in the large intestine. Acids are the best antiseptics; they have been used from time immemorial as preservatives; pickles are preserved in vinegar or acetic acid, and when milk is allowed to sour under proper conditions, the germs of putrefaction are destroyed or their activity inhibited, and it keeps a considerable time. Doubtless, in hot countries, it was this property of lactic acid which first led to milk being artificially soured with a view to its preservation as an article of food. So powerful is lactic acid in this respect that it is a custom in some countries to preserve meat by placing it in soured milk.

How can acids be applied so as to control the bacterial flora of the large intestine? Not in the ordinary way, because, when administered through the mouth, they are used up long before they can penetrate to the colon. The brilliant idea occurred to Professor Metchnikoff, of administering acid-producing germs which might work their way through the digestive system, and, reaching the large intestine, produce the acid required. After much experimenting the bacillus of Massol, Bacillus bulgaricus, was adopted as the most suitable. The Bulgarian bacillus is an extremely vigorous one, multiplying with great rapidity, and persisting in conditions that would be inimical to other microbes. The growth and development of bacteria is interfered with by the products of their own activity; thus, ordinary lactic-acid-producing organisms die when a certain amount of lactic acid has been developed; the same fate overtakes the Bulgarian bacillus, but it survives longer and is able to produce as much as two and one half per cent. of lactic acid in milk before it ceases operations. It seemed therefore the most likely to be able to survive the journey through the digestive system. Experiments fully bore out this supposition, as no great difficulty was encountered in naturalising the Bulgarian bacillus in the large intestine, not only in milk cultures, but grown in solution of malt, bouillon, etc. It thrives in all kinds of sugar, and therefore can be administered in a variety of media, very beneficial results following in many cases. Direct tests showed a large reduction of the injurious intestinal flora when the Bulgarian bacillus had been naturalised in the colon, and the bacillus persisted long after it had ceased to be administered. Specialists who have taken up the subject report the cure of many ailments through the agency of soured milk, and it seems to have entered upon a lengthening career of medical usefulness.

The fact of so many old people being found in countries where soured milk is a staple of diet naturally raises the question as to whether its general use in other countries might not have a beneficial effect on health and longevity. Its usefulness as a remedial agent in certain diseases is already demonstrated; is there not a strong probability, amounting almost to a certainty, that its consumption by people in health would tend to ward off many ailments and prolong life? Of course there will be some for whom it is not suitable; there are people who cannot eat strawberries without discomfort, but no one thinks of prohibiting the general use of the fruit on that account. In the matter of diet the person in health, if he exercises ordinary care, may be left to find out for himself what suits him. The soured milk remedy is not a disagreeable one, as, when properly prepared, the article forms both a pleasant and refreshing article of diet. The question of getting the right article, however, is a very important one. Milk is a splendid rearing ground for many bacteria, some of which are very injurious; among these may be pathological germs, the seeds of tuberculosis, enteritis, etc. The danger with soured milk is, that in the process of culture we develop the best condition for the increase of these when they preponderate, or when, through the use of bad cultures, the lactic-acid-producing bacteria are absent, or present only in small numbers. By the thorough boiling of the milk, we get rid of all living bacteria and nearly all spores or germs, and by scrupulous cleanliness in the vessels used—scalding or even boiling them, and allowing them to dry naturally in an inverted position—we greatly diminish the probability of infection with fresh injurious germs from the atmosphere. All depends on the purity of the culture employed; this can now be obtained, prepared in the most careful manner, from wholesale chemists making a speciality of its manufacture.

As we have seen, even the Bulgarian bacillus is ultimately killed by the products of its own activity, and the natural corollary is, that the life of cultures cannot be a long one. Only those cultures should be bought which are labelled with the date to which they are guaranteed to maintain their efficiency. With fresh good milk, careful boiling, scalding, and cleanliness with regard to the containing vessels, and the means of maintaining the incubating temperature for ten or twelve hours, there is not the slightest difficulty in preparing perfectly reliable soured milk. There are simple tests which will sufficiently guide the experimenter; the soured milk should not be too acid to the taste, and it has a flavour of its own by which its quality can be recognised. The litmus test-papers mentioned in the chapter on the chemistry of milk are very useful; both the red and the blue papers should be obtained and used first of all in testing the quality of the fresh milk. After incubation the soured milk should turn the blue paper decidedly red; if this does not occur, test it with the red paper; if the latter turns blue it is proof that the wrong fermentation has taken place—that putrefactive germs have gained the upper hand. The most probable explanation is, that the culture is bad, the Bulgarian bacillus is not present, or if so, only in small numbers. With these simple tests, combined with proper care, one cannot go far wrong. The Eastern nations who prepare soured milk in various forms do not exercise the care we have predicated, but they seem to make the article of fairly constant and good quality. It has been suggested in explanation that, as the ordinary flora differs in different countries, the bacterial flora varies in a similar manner, and that in these Eastern countries injurious bacteria are not so prevalent in the atmosphere as they are with us.

It is also said that the flavour of the soured milk prepared in Bulgaria is quite different from that prepared in Paris, London, or New York; one reason probably is that the "maya" or ferment used in Bulgaria contains several other organisms besides the Bulgarian bacillus, which raises the question whether a pure culture of one bacillus is the best to use.

Professor Metchnikoff found that this bacillus alone had certain defects; it attacks fat and is apt to give a tallowy taste when cream is present in the milk. He therefore associated with it another lactic-acid-producing organism, and this combination is the basis of his culture called "lactobacilline." The presence of yeasts, which occur in the Eastern ferments, has been advocated by some; the yeast in association with the lactic organisms produces a small amount of alcohol. The question of the composition of the culture will have to be fought out by the experts, but meantime, if we go to the right source, we have good enough cultures to go on with.

A good deal can be said for the use of skimmed or separated milk instead of whole milk. Cream as a rule contains far more bacteria than the rest of the milk, and we therefore start from a surer foundation when it is removed; besides, the mechanical separator, now so largely used, removes slime and other impurities from the milk, and these also are hotbeds of bacteria.

Soured milk may be taken at any time, the first thing in the morning, before or after meals, or the last thing at night. The quantity will vary with the individual, but from half a pint to a pint is a fair amount for daily use. If one wishes to have the maximum effect it is necessary for the time being to curtail the use of butcher's meat and substitute fish, yolk of eggs, and other similar foods; not much alcohol should be taken, and smoking might be reduced to a minimum. Those who cannot take even skimmed milk may use whey in which to cultivate the bacillus; it is not desirable to employ the whey which has been separated by the use of rennet, as in cheese- or junket-making. A better article is obtained by adding a very small quantity of pure hydrochloric acid to milk which has been boiled, and then filtering through a sieve, which retains the curd while the liquid whey passes through; a pinch of soda is added to neutralise the excess of acid, and, after boiling, the liquid should turn red litmus paper blue; it is then ready for the addition of the culture and incubation in the same manner as with milk. A solution of malt—the extract dissolved in hot water is convenient—may also be used instead of milk, and strongly malted bread or biscuits are excellent to take with the soured milk or cultures in other mediums, to supply food for the bacillus in the form of malt sugar. Other sugars, cane or grape, are also very useful, and may be taken in the form of fruit juices, syrups, confections, jams, sweet puddings, etc.

We lay stress on the use of soured milk or other cultures of the Bulgarian bacillus by people in health as a probable preventive of disease and a possible agent in the lengthening of life, but it may be of interest to give a short account of its use by medical men in the treatment of various ailments. An English authority on the subject, Dr. Herschell, states that the symptoms of the poisoning of the system by the toxic substances produced by injurious bacteria in the large intestine may include headaches, misery and depression of spirits, drowsiness and stupor, giddiness, dimness of sight and dizziness, fatigue without obvious cause, both of the muscles and brain, fear, panic, and nervousness, disagreeable sensations in the limbs or face, such as numbness, tingling, or prickling, crawling sensation of weight or of heat or cold, dyspepsia of the sort where there is a deficiency of hydrochloric acid and pepsin in the gastric juice, accompanied by flabbiness and loss of power in the muscles of the stomach, and characterised by flatulence, nausea, loss of appetite, with discomfort and weight after food, furred tongue, emaciation, earthy colour of the skin, offensive perspiration and the other signs of biliousness, enlargement of the liver, and anæmia. These symptoms may have other causes, and when one or several of them are present a chemical and physical examination of the urine and fæces is necessary to prove that they have resulted from auto-intoxication. When this is shown the soured milk treatment is indicated, and many striking cures are detailed as witnesses to its efficacy. The liver and kidneys are the natural guardians of the body against the toxines we are speaking of, and frequently they are over-strained; the soured milk treatment greatly lightens their load. In malignant disease of the stomach, soured milk will frequently be retained when all other foods are rejected. In cases of neurasthenia and gout it has also proved of value, and in the "run-down" condition which is so common in middle life. Chronic diarrhœa and certain forms of constipation have in numerous instances yielded to the treatment, the whey culture being usually found the most suitable. Then, in some forms of anæmia, the lactic acid cultures have proved most successful, and, as a means of rendering the gastro-intestinal track aseptic previous to operations, they have proved of considerable value.

If all this has been accomplished in a year or two, what may not we look forward to in the future when more extended use and experiment shall have more fully exhausted the possibilities of the cure? But if we follow the example of the different nations who have so long used soured milk as a regular article of diet, does it not seem probable that we may eliminate some, at least, of the causes of ill-health that call for the intervention of the doctor?

The human organism is by no means perfect; we have within us many defective parts, and some organs whose working seems to be against the welfare of the economy. It has now been clearly shown that one of the chief of these is the large intestine, as to the use of which only vague and unsatisfactory theories have been formed. There can be no doubt as to the damage which it frequently inflicts on the system, and, thanks to the researches of Professor Metchnikoff and other investigators, we seem to be in possession of a natural remedy which is sufficient to deal with the evils it produces.

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