The liver is one of the most important of our organs. As Professor Hemmeter, of Baltimore, says, “The liver is an organ secondary in importance only to the heart. Living things can exist without stomachs. They can live for forty days without eating, but mammalia can only live a few days, sometimes not twenty-four hours, without a liver.” The importance of the functions of the liver is illustrated in this picturesque remark of Dr. Rovighi[172]: “Like unto Minos in Dante, the liver tests the conscience of those that want to enter, and knows their sins.”
We introduce into our stomach and intestines a number of poisonous substances which, if injected into our blood, would kill us, or at least, cause grave intoxication. Yet because they are taken by the mouth they are harmless, and the reason for this strange phenomenon is that they must pass through the liver, being brought to this organ from the intestines through the portal vein, and are there destroyed. This is illustrated in the case of the Indian snake charmers, who acquire immunity against snake-bites after having first sucked the poisonous fang of the snakes and absorbed the toxin via the intestine. They thereby gradually accustom their body to this terrible poison, which, taken in this manner, is far less harmful, since it passes through the liver. That the liver destroys various poisons was first shown by our esteemed friend, Prof. Paul Heger,[173] of Brussels University, who demonstrated by experiments that nicotin added to blood soon disappeared after it had been passed through the liver artificially. After this remarkable discovery other authorities have found reason to state that the liver also destroys other poisons, in particular alkaloids: strychnine and atropine (Professor Roger[174]), hyoscyamine (Heger and Buys[175]), quinine, morphia, curare (Lussana). According to Schiff, and Lautenbach, alkaloids undergo a chemical change under the influence of the liver. As Slowzoff[176] found, the liver also protects us against poisons such as arsenic; therefore we can understand why persons suffering from hepatic disease cannot tolerate arsenic. This should be taken into consideration when we are treating patients with cacodylates, or with atoxyl.
It has, however, been maintained by Zagari that this antitoxic action of the liver fails in the case of bacteria and, according to Professor Roger, especially with bacterial toxins in old cultures.
Yet other authors have shown that the liver probably has an antitoxic action against bacteria and their toxins. Thus, Professor Adami, of Montreal,[177] by experiments with a minute diplococcus similar to that which is found in Pictou’s cattle disease, and Sir Lauder Brunton, and Dr. Bokenham,[178] have shown that the lethal action of diphtheria toxin is greatly diminished during the circulation of this toxin through the liver, and also that the juice from such a liver has a slight antitoxic power. These authors have also shown that the bile from such a liver has a slight antitoxic action. They consider that the antitoxic power of the liver does not depend upon the blood present in the organ, but on the liver-tissue itself.
It has been shown that the liver excretes into the bile poisons which it arrests during their circulation through the portal system. This has been shown by Lussana in the case of curare. That poisonous substances are excreted into the bile is shown also by the immunizing experiments of Professor Koch against bovine plague. He employs the bile of animals which died of plague. This contains attenuated plague bacilli, of which Professor Koch makes use in his experiments.[179]
Dr. Fraser[180] has shown that when increasing doses of snake-venom are injected into an animal a condition of immunity is brought about, so that finally fifty times the dose which would have proved fatal at first, becomes innocuous. As Fraser found, the bile of such animals contains an antivenine, and he made use of this bile as an antidote against the original venom.
These experiments prove that the bile contains poisonous substances, including pathogenic bacteria in an attenuated condition, and also that it has antitoxic properties. Thus we may understand how it can neutralize putrefactive products from the intestines. Not only bacteria, but all the various kinds of poison which the liver destroys, are eliminated by the bile; hence the importance of a free circulation of this fluid. The liver serves as a depot for metallic substances like iron and copper, and also for the more dangerous ones such as lead, mercury, arsenic, or antimony. After first keeping them in storage, it then attempts to eliminate these noxious substances. According to Slowzoff and Bamossi, the various poisonous metals and alkaloids enter into combinations with the proteid bodies of the liver. Animals that have been richly fed have been found to be better protected against these poisons because of their livers being richer in proteid contents and glycogen.
The liver also protects the body against the numerous toxic products formed in the stomach and intestines during the process of digestion and assimilation. The most important of these are the carbamins and ammonia salts, which would be injurious to us if the liver did not protect us by converting them into urea.
When the liver is excluded from the circulation, as Nencky and his pupils have done by establishing an Eck fistula, toxic symptoms arise when the animals are given albuminous food, and these symptoms can only be explained from the fact that the liver is unable to destroy toxic products. The more albuminous food taken, the more marked are the symptoms of intoxication.
The liver aids in the transformation of the poisonous end-products of proteid metabolism by bringing about the combination of the toxic end-products with sulphuric acid (Baumann, Emden and Glaesner). Thus these dangerous substances are eliminated as ethereal sulphates, which are practically harmless. Even when these ethereal sulphates are present in large amounts in the urine there may be no symptoms of auto-intoxication.
When the liver is extirpated, a condition of acidosis arises, and a large quantity of ammonia is eliminated, which is produced in order to neutralize the acids present. The liver protects us against acids formed in the organism. After eating a quantity of meat, we would be menaced by the acids formed through its decomposition, were the liver not active.
We can prevent acidosis if we eat a considerable amount of carbohydrates, at least 100 grammes a day as Hirschfeld has proved. It has been shown by Waldvogel that these carbohydrates do not prevent acidosis if they are given by a method which precludes their passage through the portal circulation,—e.g., subcutaneously.
As we have seen above, the liver receives an enormous amount of toxic products from the stomach and intestine, which it transforms or destroys. Like any other organ which is overworked, the liver may undergo certain changes when continually subjected to a strain, and great quantities of these toxins might be able, after a long-continued action, to alter the liver tissue. Such a condition we may note in gastric and intestinal diseases, especially in those cases where large amounts of fatty acids are formed.
Bouchard found an enlargement of the liver in 23 per cent. of all his cases of dilatation of the stomach.
We can understand that when fatty acids, as a result of gastro-intestinal disease, pass for a long time through the liver, they may destroy the delicate epithelium of this organ. Boix demonstrated this by experiments. By feeding animals with lactic, butyric, and acetic acids, he produced hepatic cirrhosis.
So long as the liver is healthy it is able to withstand the constant inflow of toxins and will transform them into less harmful compounds. But when the liver is altered, as in cirrhosis, things are different. We then find a diminution of urea, and an increase of ammonia. Happily such a condition arises only when there are considerable anatomical and histological changes in the liver.
Salaskin and Zaleski have shown in animals that when there are serious anatomical changes in the liver, the ammonia is increased, and the urea is diminished. We may suppose that in old age, when the connective tissue is more or less increased and important liver elements destroyed, a similar decrease in the urea formation may take place just as in chronic cirrhosis.
That in diseases of the liver toxic products are formed and eliminated by the urine in increased amounts, has been shown by Professors Bouchard[181] and Roger. They found that the urine of patients suffering from diseases of the liver is more toxic than that of normal persons.
That the normal urine is toxic has been proved by Séglas and Vauquelin,[182] and also by Bocci.[183] Bouchard has designated as the urotoxic unit the quantity of urine necessary to kill an animal weighing 1 kilogramme, and as the urotoxic co-efficient the relation of the urotoxin eliminated in twenty-four hours to the body weight of the animal. This latter, then, indicates the quantity of urotoxins a man eliminates in twenty-four hours.
All these calculations of Bouchard have had no great success, however, for many authorities, as Gumprecht,[184] Heymans v. d. Bergh, etc., have shown that the toxic effects of the injected urine may be explained in part by the difference in osmotic pressure between the injected urine and the blood.
Still the fact remains that the urine of many cases of liver disease has been found to be more toxic than the urine of other persons.
When the liver is damaged it cannot destroy poisons in the normal manner, as was shown by experiments. Thus, the liver cells have been experimentally injured when it was found that such a liver was not able to destroy strychnine as well as a normal liver. Very important findings have been made by Roger and Gamier.[185] They have ascertained that privation, bad nutrition, etc., can also lower the vitality of the liver and diminish its antitoxic properties.