The intestines contain billions and billions of microbes, their number increasing downward throughout the length of the intestine. The duodenum contains the least, and in some parts of it there are none at all.
The presence of these bacteria is a great necessity to us, as without their assistance we could not exist, for they take an active part in intestinal digestion and help to form the intermediate substances, especially from albuminous food and fat, for our nutrition. They also assist fermentation and thus induce a better peristalsis of the intestines, by which the contents are expressed.
That animals cannot exist without cultures of bacteria in the intestines is shown by the experiment of Schottelius, who demonstrated that young chickens could not thrive on a sterilized nutrition, and Nuttall and Thierfelder had great trouble in keeping their guinea-pigs alive when feeding them for a time on sterilized milk.
All those bacteria which are found in the intestines are, we may say, innocuous; they assist digestion and do no harm. But among such are often virulent bacilli against which, under normal circumstances, we are well guarded, as the epithelium of the intestines is so wonderfully arranged that so long as it is in a healthy condition it does not admit the passage of these microbes; but in the aged, or in those exhausted by debauchery or previous disease, or when there is an inflamed condition of the intestines, stagnation of hard masses of fæces for a very long time cause mechanical lesions of the epithelium when, conditions now having changed, nothing will prevent these microbes from entering the walls of the intestines and either cause disease, like typhoid or tuberculosis, or from passing through and entering into the blood.
Besides these dangerous bacteria many other harmful substances pass from the stomach down into the intestines, whence they are taken up by the portal vein and brought to the liver. When the latter is in good condition so much the better for us, but when they arrive in too large quantities, or when the liver is more or less degenerated, as in old people, drunkards, gourmands, etc., then trouble arises.
When the number of bacteria in the intestines is much greater than usual, certain dangers arise from such a condition, as thereby the immigration of bacilli into the bile-duct is facilitated causing inflammation of the gall-ducts and gall-bladder, and subsequently gall-stone disease. Further consequences of such a condition may be the closure of the bile-duct, and then no bile can reach the intestines. The presence of bile, however, is very important, for, according to current opinion, this exerts an influence on the checking of putrefaction in the intestines. Bile is a natural antiseptic of great efficacy, and has also a stimulating effect on the nerves of the intestines, promoting their peristaltic movements.
It would, therefore, greatly interfere with the useful work of those organisms normally present if we permitted the formation of enormous quantities of bacteria, especially of such as are harmful to us; so we must endeavor to eliminate them and not give them the opportunity to turn against us, and we must do all in our power to keep the peristalsis of the bowels in good working order so as to prevent any stagnation of their contents, as such a stagnation, in addition to favoring the growth of bacteria, also facilitates the development of auto-intoxication. Even if it is true that most of the end-products of proteid food in our intestines, like indol and skatol, are not able to produce severe poisoning if injected into other animals; still there is no doubt that in medical practice not infrequently cases are observed where the retention of all these products together results in very grave conditions. Thus Ewald[212] has published the case of a woman who, for about a month, retained the contents of the bowels and in consequence presented a serious condition of intoxication; after eliminating a large quantity of fæces—pitch dark—she recovered and the symptoms of intoxication disappeared. Senator also published a very interesting case of auto-intoxication with hydrothionuria.
We often have occasion to note cases of persons having no bowel action for two to three days, who then complain of headache, loss of appetite, and various nervous symptoms, neurasthenia, etc., all of which may, perhaps, be regarded as of reflex origin; but when we see in such people a yellow or yellowish-gray complexion which, after a good purge, resumes its clear condition, clinically, we regard it as auto-intoxication.
Even if, as already mentioned, most of the elements of albuminous catabolism are not toxic if injected into animals, still, occasionally, toxic products can be formed, such as cholin and neurin, which come from the former. These elements arise from decomposition of the lecithin, which, of our various foodstuffs, is contained in the greatest quantity in eggs; and these substances can provoke serious nervous symptoms. In such cases there is, of course, a stagnation of long duration of the bowels, but such a condition as the latter can arise without a stricture or obstruction, although these are the most frequent causes. Another toxic product is the pepto-toxin of Brieger.
Stagnation takes place in sluggish bowels. As a general rule, fæcal movement is caused by peristalsis of the intestines, which consists of circular contractions of the bowel by which the contents are propelled toward the end of the same; besides these movements there are also pendular or vermicular contractions of certain parts of the intestines; all these movements also assist the admixture of the chyme with the juices of the intestines. All these contractions are caused by impulses from the nerves which lie in the walls of the intestines, the plexus myentericus; they can also be provoked by impulses coming from the central nervous system.
The nerve ganglia that lie in the walls of the intestines can be influenced mechanically by the contents of the intestines, when such are bulky, and also when they are fermenting; therefore, the bacteria, by promoting fermentation, also aid in peristalsis. The bulky condition of the bowel contents can be best induced by food of the vegetable kingdom through its cellulose contents, of which tissue the cells of plants or fruits are largely formed. When these irritating agents act on the nerve filaments in the intestines, the bowel will contract and expel its contents.
But when food contains no irritating substances and is easily assimilated without forming residues, or when the innervation by the vagus is sluggish and the peristaltic movements are slow, the contents of the intestines can remain longer, especially in the haustra of the intestines. It may be that the bowels move every day, but that does not prove that everything in the intestines has been expelled therefrom, for some amount of fæces can yet remain in the haustra of the intestine even for many days; so that in such cases there is still a constipation of one part of the bowels. We have observed, personally, and on patients, that, after a good opening of the bowels, when a purge is given—for instance, directly after a meal—a short time afterward there has been another copious discharge that had evidently remained behind. Thus, no doubt a retention of fæces, and sometimes a condition analogous to auto-intoxication, can be caused in people who have the bowels opened every day, although not to the extent of those having obstruction or habitual constipation.
To avoid such a condition a good purge should be taken at regular intervals, say once a week, even by persons who have a movement daily, in order to eliminate matter which may have remained. It will not be necessary, naturally, to use a too powerful purgative, but one adapted to the necessity of the case; taking, as a rule, such a purge as will act a little better than the ordinary bowel movement, and graduated according to the strength of the person so using it.
Before closing this chapter we must also briefly insist upon the importance of the fact, that the secretions of the intestine and of its glandular annexes have also an anti-bacterial and antitoxic action. Very important is the rôle of the bile for the disinfection of the intestine, as it contains two acids, the glycocholic and taurocholic, which possess highly anti-fermentative properties. As already mentioned, the bile also assists in the assimilation of fat, and also exercises a stimulating action on the peristalsis of the intestines.