the name of amphopeptone to the total quantity, antipeptone to that part not attacked, and hemipeptone to that part which was further broken down. He surmised that the splitting of the albumin molecule took place earlier in the process, and he made attempts to isolate intermediate substances, which he called amphoalbumoses. That part of the albumin not attacked was called antialbumid; very strong trypsin converts it into antipeptone, as was observed by Schützenberger in 1875. It is really, however, converted into antialbumose or deuteroalbumose, and Kühne gave the following diagram to show these results ::

Now, however, it is known that no antialbumose is formed, but only antipeptone.

The characteristic changes produced by trypsin have been more carefully studied with fibrin. As with pepsin, this substance has also the property of taking up the ferment, and a method of obtaining trypsin in a relatively pure condition is thus obtained.

The fibrin first dissolves, but does not swell up as it does in peptic digestion, being rather eroded from the outside. The solution has the property of a globulin, but no globulin is formed from serum-albumin, etc., also no syntonin nor a product corresponding to that formed in peptic digestion. Primary albumoses are not formed, but

deuteroalbumose is obtained directly, then amphopeptone, and finally antipeptone and hemipeptone, of which the former constitutes rather more than half of the total quantity of the peptone. The further action of trypsin consists in the conversion of hemipeptone only into aminoacids, and a chromogen, which was first observed by Tiedemann and Gmelin in 1831, and called tryptophane by Neumeister. This chromogen forms a very suitable substance for determining the progress of tryptic digestion.

According to Nencki, tryptophane, called proteinchromogen by Stadelmann, can be brominated, when it gives rise to two substances. These, on removal of the bromine, have similarities on the one hand to hæmatoporphyrin and to bilirubin, and on the other hand to melanin; he therefore considers them the mother substances of the animal colouring matters, even of hæmoglobin.

Hopkins and Cole have quite recently isolated tryptophane, and have given it the formula C11H12O2N2 ; it gives the Adamkiewiez reaction, and yields skatole and indole when heated; it is probably indoleaminopropionic acid or skatoleaminoacetic acid.

The chief acids obtained are leucine, tyrosine or p-oxyphenylaminopropionic acid, aspartic acid, and glutamic acid; besides these, Drechsel and Hedin have found lysine or a, ɛ-diaminocaproic acid, and lysatinine, which is now known to be a mixture of lysine and arginine or d-guanidine-a-aminovalerianic acid; Kutscher has obtained histidine, CH,ONз.

Glycocoll, long known as a decomposition product of gelatine, has been found by Spiro among the decomposition products of albumins.

Emerson has obtained p-hydroxyphenylethylamine, which is formed from the tyrosine, which loses carbon dioxide, its amount decreasing as the quantity of this substance increases.

Ammonia, according to Hirschler and Stadelmann, is given off in small quantities when trypsin acts upon albumins. Its amount has been determined by Dziergowski and Salaskin, who obtained it both in peptic and tryptic digestion. For the different albumins its amount varies, but in every case it is greater than that liberated by dilute acid or alkali, and it never corresponds to the total aminonitrogen of the albumin.

Lea states that the removal of the products has an influence upon the digestion by trypsin, which is more rapid and complete than that of pepsin.

Nencki has stated that he has obtained xanthine, guanine, hypoxanthine, and adenine in the digestion of fibrin by trypsin; but Kossel denies this, saying that they are products of nucleins resulting from the entanglement of leucocytes in the fibrin.

The following diagram shows the formation of the principal products :—

leucine, tyrosine, aspartic acid, glutamic

acid, lysine, arginine, histidine, ammonia.

Lately, investigations have been carried out as to the nature of antipeptone. Siegfried and Balke considered it to be a chemical individual, and the former investigator regarded it as identical with his carnic acid, C10H15O5N3. Kutscher, on the other hand, maintains that antipeptone is not a chemical entity, because he has obtained from it a mixture of substances which can be separated by phosphotungstic acid into an acid part and a basic part; the basic part consists of histidine, arginine, and another unknown base, and from the acid part aspartic acid was obtained. Siegfried states that antipeptone can be obtained pure from impure antipeptone by precipitation with alcohol, and he has since isolated two acids from antipeptone which he designates a-antipeptone, C10H17O5N, and B-antipeptone, C11H19O5N3; they were not equal in amount, and they do not give quite the same products on hydrolysis with stannous chloride and hydrochloric acid; neither of them is identical with his carnic acid; he thus shows that antipeptone is not a mixture of substances, as stated by Kutscher, though his two acids can give those substances on hydrolysis.

The proteids are generally quickly decomposed by trypsin into their components, and the albumin digested like fibrin; e.g. casein is almost completely digested, giving tyrosine, casein albumose, and casein antipeptone. Biffi, who investigated this decomposition, found that the phosphorus was partially converted into phosphoric acid, and partially into another compound not precipitated by magnesia mixture.

The nuclein of nucleoproteids is peptonised with the separation of nucleic acids, and then of nuclein bases,

which Bokay states resist the action of trypsin, though Kutscher, as above mentioned, found xanthine, hypoxanthine, and guanine.

Of the albuminoids, only collagen and elastin are attacked by trypsin; the native collagen, however, is only changed when it has been first transformed into gelatine, or gluten, by the action of steam or acids, by the latter of which it is changed in peptic digestion.

Chittenden and Solley state that gelatine is converted into protogelatose and deuterogelatose, and that no gelatine peptone is formed when putrefactive changes are very carefully prevented from occurring. Chittenden and Hart state that no peptone is formed from elastin, but that protoelastose and deuterogelatose are both formed.

From gelatine Nencki states that he has obtained gelatine peptone, leucine, glycocoll, and ammonia; and from elastin Wälchi has obtained glycocoll, leucine, aminovalerianic acid, and ammonia.

The lecithines are also decomposed by pancreatic juice like fats, and are converted into their constituents, viz. choline, glycerophosphoric acid, and fatty acid. The choline, according to Hasebroek, is converted into carbon dioxide, marsh gas, and ammonia, the same products being also produced by bacteria when no oxygen is allowed to be present.

Kossel and Matthews have investigated the action of pepsin and trypsin on protamines (salmine and sturine), and have found that they are only attacked by trypsin, which converts them firstly into protones, and then partially only into hexone bases (lysine, arginine, and