THE DECOMPOSITION PRODUCTS OP PROTEIDS. 63 



plex proteids of the blood and tissues at the other, we 

 are still in the region of conjecture. 



There is, however, another series occurring in the 

 alimentary tract which has yielded more plentiful results. 

 As early products we have been taught to distinguish 

 proteids, albuminates and peptones, and many simpler 

 nitrogenous bodies like leucine and tyrosine. 



It is mainly, however, from changes brought about by 

 the treatment of proteids with varying reagents that we 

 have gained our greatest knowledge on this subject. In 

 this respect the aim must be to isolate all the products pro- 

 duced during the various decompositions, and so obtain a 

 complete series which will show us, step by step, the suc- 

 cession of changes the proteid has undergone. It is my 

 intention to indicate in this paper how some of these steps 

 have been attained, and to point out the arguments which 

 may be based upon the knowledge thus gained. 



Most of the researches as yet carried out have investi- 

 gated the early or the final products. The changes pro- 

 duced by the first action of the different reagents have 

 resulted in the formation of albuminates, proteoses, and 

 peptones. Into these changes it is not necessary to enter 

 in detail. In considering the final products formed, it will 

 be convenient to arrange the subject under the headings of 

 the different methods employed. 



1. Alkalies. Mulder 1 treated albumin with caustic 

 potash, and obtained a body to which he gave the name 

 "protein," and which he considered as the base of all 

 albuminous material. He also described various com- 

 pounds of this substance such as sulpho-proteic acid, 

 protein, etc., but most of his assertions have been dis- 

 proved by Liebig," 2 who showed that "protein" is a body 

 which we now know as alkali-albuminate. Pavy states that 

 by the action of caustic potash upon albumin he has been 

 able to split off a body of an amylose nature, which on 

 further treatment yields a reducing sugar. 



1 Journ. f. praktische Chemie, vol. 16, p. 129, and vol. 17, p. 312 ; also 

 Liebig's Annalen der Chemie, vol. 31, p. 129. 



2 Liebig's Annalen der Chemie, vol. 57, p. 132. 



