DIGESTION OF THE ALBUMINS. 183 



been modified in several important particulars. Much of our present 

 knowledge is due to the Strassburg school and to the researches of 

 Ernil Fischer and his pupils. It has thus been shown that quite 

 early in the course of digestion a certain proportion of nitrogen is 

 split off from the albuminous material in the form of ammonia or of 

 a compound which yields ammonia on distillation with magnesia. 

 At first this is small in amount ; subsequently it increases and for 

 a time it remains constant. This nitrogen represents products 

 which no longer give the biuret reaction and which undoubtedly 

 are closely related to the end-products of digestion. Coincidently 

 the primary albumoses appear, of which we now recognize three. 

 These are proto-albumose, hetero-albumose, and a third, which Pick 

 has designated as gluco-albumose, 1 from the fact that it contains the 

 carbohydrate group, which is absent in the first two mentioned 

 (in the case of fibrin, at any rate). 



On further digestion the primary albumoses give rise to secondary 

 or deutero-albumoses, of which several forms exist. These are desig- 

 nated as deutero-albumose A and A', deutero-albumose B and B', 

 and deutero-albumose C. These in turn give rise to bodies which 

 in part give the biuret reaction and in part not. Collectively these 

 are termed polypeptids and, in part, no doubt, they correspond to 

 Kiihne's peptones. Many of the simpler forms have been made 

 synthetically (see p. 000), but the more complex bodies, which are 

 more closely related to the albumoses, are comparatively unknown. 



Pick speaks of an A and a B peptone which result from the second- 

 ary albumoses (with the exception of deutero-albumose C), and which 

 differ from each other in their behavior toward alcohol and iodo- 

 potassic iodide in saturated ammonium sulphate solution, peptone A 

 being precipitated by both reagents, while peptone B remains in 

 solution. A further examination of the bodies in question has not 

 been made. 



Siegfried and his pupils describe two pepsin peptones which were 

 obtained from fibrin. They are designated as pepsin-fibrin peptone 

 a and }. By losing water the /9-peptone passes over into the - 

 peptone : 



On further decomposition with trypsin the a-peptone then yields 

 ty rosin, arginin, and, according to Siegfried, also two other peptones, 

 which he terms trypsin-fibrin peptone a and /9. He accordingly 

 points out that the a-peptone is a true ampho-peptone in the sense 

 of Kuhne. 



Of the nature of these products, however, very little is known. 

 They manifestly are polypeptids in the sense of Fischer. 



1 The term first used for this was deutero-albumose B or albumose Ba. Hofmeister sug- 

 gests synalbumose as a better term, since there is a possibility that albumins may exist which 

 may yield a primary albumose of this order containing no carbohydrate group" (casein), and 

 that ou the other hand albumins which are very rich in carbohydrate groups may possibly 

 form proto- and hetero-albumoses in which these are represented. 



