Saliva in dis

ease.

branes of the cavity of the mouth, constitutes mixed saliva. This can be collected in quantity by irritating the fauces with a feather, and producing vomituritions. It does not reduce alkaline copper solution, but retains a little copper oxyde in solution when cupric salt and alkali only are added. It transforms starch into sugar, so that chewed pap after some standing, with cupric sulphate and caustic potash, at 70° C, yields red copper suboxyde. It does not change cane-sugar into invert sugar, and thus differs from yeast. The quantity of mixed saliva secreted by a man in 24 hours varies between 300 and 1500 grammes ; it may be greatly increased by excitants, and irritating medicines and poisons.

Little is known of saliva in disease, but the investigations of the future promise further results. In diseases, ingredients. such as salivation under the influence of mercury,

Anomalous

Digestion of starch.

rhodanates disappear. The saliva then contains mercury. Many medicinal salts pass easily into the saliva from the blood, such as iodide and chlorate of potassium, and when used long in quantity produce slight salivation. In diabetes the saliva contains lactates, but no sugar. In the paralytic saliva of hysteric persons leucine has been found. Acid saliva seems to contain lactic acid, and is of course anomalous. The presence of urea has been alleged, but not proved with certainty. In hydrophobia the saliva is the bearer of the contactpoison by which the disease is propagated to other individuals.

While the saliva influences starch as indicated, and does not lose its action by the admixture of acid of

It

the liver.

the concentration of the gastric juice, it certainly, under ordinary circumstances, does not transform the whole of the starch into sugar. The gastric juice has no influence on starch; the pancreatic juice a trifling influence in the same sense as saliva. Deducting all sugar and lactic acid to be met with, it is necessary to assume that other products are formed, which yet elude analysis. Do any of these products find their way into the liver, and are these transformed into glycogen ? Glycogen is a kind of dextrine, which was discovered Glycogen of in the liver by Bernard and Hensen. It occurs in three forms, of which one of the formula C.H10O5, is powdery, two others, C,H12O6, and C8H1407, are gummy. polarises to the right four times more intensely than dextrose sugar. With a solution of iodine in iodide it gives a dark red colour. It dissolves copper oxyde without reducing it. By sulphuric and hydrochloric acids, saliva, pancreas juice, serum of blood, and cold prepared extract of liver, it is transformed into dextrine and ultimately into sugar. Many physiologists have endeavoured to explain the source and destination of this matter, but as yet without any very complete success. Regarding its origin, it has been found that it could not be formed from sugar, as the portal blood did not contain any. It was not formed from fats. Animal food enabled animals to form it, whence the conclusion was drawn that glycogen originated in albumen. Seeing that the liver decomposes albumen, as proved by the constitution of the bile, this idea has much in its favour, but the experiments upon which it is based admit of different interpretation. Muscle

Destiny of glycogen.

Mal-assimilation of starch.

frequently contains dextrine, always inosite (a particular kind of sugar), and lactic acid. All these might

enable the liver of the animal which eats the flesh to form glycogen. At present it is uncertain from which material the liver forms glycogen; possibly it is formed out of starchy and albuminous matters at the same time; at least most of it is formed (up to 12 per cent. of the weight of the liver in fowls) when these two kinds of food are digested together in large quantity.

As the dead liver was found to transform glycogen quickly into sugar, and as some sugar could be found in hepatic blood, it was concluded that glycogen is transformed into sugar, and passes into the blood, to be there oxydised or changed as required. This view, upon which was based an entire theory, called that of the glycogenetic function of the liver, was received for some years by physiologists in general, until one of its greatest admirers, Pavy, believed that he had discovered it to be erroneous. According to him no sugar is made in the liver in the living healthy body. I showed that his experiments admitted of such variation as to prove either his or Bernard's doctrine. At present the bulk of evidence goes to show that, as a portion only of the starch in the intestines is transformed into sugar and passes into the chyle, so a portion only of the glycogen of the liver is transformed into sugar and passes into the blood. Quantitative experiments on a large scale, combined with the chemolytic method of research, will alone be able finally to decide the matters under discussion.

When sugar in considerable quantity exists in the

blood, the body cannot deal with it, and excretes the sugar unchanged. Such a condition constitutes the disease termed diabetes, which appears to be a much Diabetes. more complicated disease than its main symptom taken alone would seem to indicate. The oxydation of sugar only is diminished or not accomplished, that of the albuminous substance and fats is rather increased, sometimes enormously so; therefore the carrying power of the blood-corpuscles for oxygen cannot be diminished as has been supposed lately, at least not in all cases of diabetes. There must be a perversion of chemical agency, as proved by the appearance of lactic acid in the saliva and of acetone in the stomach and the urine. On the whole there is at present neither a plausible theory nor a rational treatment of diabetes, as evidenced by the fact that noted physicians now maintain that diabetic patients eating promiscuously everything are better off than patients who abstain from starch and confine themselves to the anamylic diet so elaborately prescribed by Bouchardat. sugar may be made in the liver or in the muscles, it may be the effect of a change of nervous influence (as suggested by the artificial diabetes of animals after wounds of the fourth ventricle of the brain), or of a failure in the supply of a ferment capable of transferring oxygen to it. The sugar when once in the diabetic blood appears not to be increased or decreased by standing of the drawn blood out of the body, the blood consequently contains perhaps no glycogen. This was ascertained by a special experiment, made upon the blood of a diabetic patient.

The

Digestion of the food in the stomach.

Pepsine.

The comminuted food mixed with saliva arrives in the stomach and excites this organ to a mechanical and chemical action, termed digestion. The many little rennet glands situated in the walls of the stomach Gastric juice. secrete a liquid termed the gastric juice, which in man contains 994-6 per mille of water and 5.39 of solid and permanently fluid ingredients other than water. Of these 30 are pepsine, 0.2 hydrochloric acid, with which perhaps a small quantity of lactic acid is mixed, and chlorides of the alkalies, with some phosphates of earths. Singular is the presence of some calciumchloride in the juice. The juice has been examined mainly as obtained from persons who by accident had fistulous openings in their stomachs, and upon dogs upon whom such fistulas had been formed by operative interference. This led to the formation of artificial juice, which requires the addition of natural pepsine, and is therefore only in part artificial. It serves, however, for the purpose of studying stomach digestion upon many kinds of food, and of supplying a kind of remedy in diseased conditions in which the natural juice is supposed to be deficient.

Gastric fistula.

Power of gastric juice.

This gastric juice possesses the power of dissolving or reducing to a liquid state albuminous substances, which are either by preparation, such as boiling, or by nature, insoluble in water. Albumen, caseine, fibrine, syntonine, the albuminous substances of vegetables, gluten, and the collagene tissues or gristle, are under the influence of gastric juice, or of a mixture of pepsine and hydrochloric acid, dissolved to thickish