CHEMICAL BASIS OF THE ANIMAL BODY. 49 



position-products of several proteid molecules, and thus throw no light 

 on the structure of any one. And the matter is still further compli- 

 cated by the fact that the final products of any given decomposition 

 do not at all necessarily represent the primary mode of breaking down 

 of the proteid molecule ; many of them may be the outcome of some 

 secondary decomposition of the first-formed products. It may hence 

 suffice to give a short account of the more generally important re- 

 searches on the decompositions of proteids and to refer the reader for 

 details to some larger work 1 . 



The products of the decomposition of proteids by acids (HC1) have 

 been elaborately studied by Hlasiwetz and Habermann 2 . These 

 observers subjected proteids (casein) to the action of boiling concen- 

 trated hydrochloric acid in presence of stannous chloride for three 

 days. From the fluid thus obtained they were able to separate out by 

 repeated crystallisations leucin, tyrosin, glutamic and aspartic acids 

 and ammonia; the mother liquor from the above yielded no further 

 well-defined substances. Schiitzenberger 3 , treating proteids in presence 

 of a little water with an excess of baryta in sealed tubes at 200 250, 

 observed a more profound breaking down of these substances as judged 

 by the products of their decomposition. In addition to the products 

 described by Hlasiwetz and Habermann he obtained small quantities 

 of carbonic, oxalic and acetic acids, together with other amido-acids 

 homologous with leucin, amido-acids of other series, leucei'ns 4 , gly co- 

 protein, tyroleucin 5 , &c. The chief difference in the results obtained 

 by the two sets of observers turns upon the non-occurrence of carbonic, 

 oxalic and acetic acids among the products of the action of hydro- 

 chloric acid. Drechsel 6 has however shown that if the non-crystallisable 

 residue from Hlasiwetz and Habermann's experiments be appropriately 

 treated with baryta in sealed tubes it readily yields carbonic acid, so 

 that the difference may turn out after all to be more apparent than 

 real. Interesting as are the above researches they do not as yet enable 

 us to form any clear idea of the probable molecular composition of 

 proteids. According to Schiitzenberger the relative amounts of car- 



1 Ladenburg's Handworterbuch d. Chem. Bd. in. S. 541. Beilstein's Hdbch. d. 

 Chem. Bd. in. S. 1258. 



2 Anzeig. d. Wien. Akad. 1872, S. 114; 1873, Nr. 15. Ann. d. Chem. u. Pharm. 

 Bd. 159, (1871), S. 304, Bd. 169, (1873), S. 150. Jn. f. prakt. Chem. (2) Bd. vn. 

 S. 397. See also E. Schulze, Zt. f. physiol. Chem. Bd. ix. (1885), Sn. 63, 253. 



3 Ann. de Chim. et de Phys. (5 Ser.) T. xvi. (1879), p. 289. Bull, de la Soc. Chim. 

 xxin. 161, 193, 216, 242, 385, 433 ; xxiv. 2, 145 ; xxv. 147. Also in Chem. Centralb. 

 1875, Sn. 614, 631, 648, 681, 696 ; 1876, S. 280 ; 1877, S. 181. Compt. Rend. T. 101, 

 (1886), p. 1267. See also Nasse, Pfliiger's Arch. Bde. vi. (1872), 589; vn. 139; 

 vm. 381. 



4 Compt. Rend. T. 84 (1877), p. 124. 

 15 Ibid. T. 106 (1888), S. 1407. 



6 Jn. f. prakt. Chem. (N. F.) Bd. xxxix. (1889), S. 425. 



F. d 



