50 PROTEIDS. 



bonic acid and ammonia which make their appearance are the same as 

 would have arisen from a similar treatment of urea with caustic baryta, 

 and from this and the fact of the preponderating appearance of amido- 

 acids by the action of the alkaline oxide, he regards the proteids as 

 complex ureides : that is to say as combinations of urea with amido- 

 acids belonging to several series such as the leucic and aspartic 1 . 

 In support of this view the work of Grimaux 2 may be mentioned. 

 By fusing together aspartic anhydride and urea he obtained a substance 

 resembling a proteid in several of its reactions, and yielding aspartic 

 acid, carbonic acid and ammonia by treatment with baryta. It has 

 not however as yet been shown that this substance can be made to 

 yield urea, and further, no one has ever succeeded in obtaining urea as 

 a direct product of the decomposition of a proteid. Further, as against 

 the view of the ureide nature of proteids, Low's views as to the 

 probable non-existence of amido-acid residues in the proteid molecule 

 must not be lost sight of 3 . 



The older statements of Bechamp 4 and Bitter 5 as to the formation of urea from 

 proteids by the action of potassium permanganate are erroneous 6 . The most recent 

 refutation of their views is due to Lessen 7 , who finds that traces of guanidin may 

 make their appearance but no urea. This substance might however be easily 

 mistaken for urea since its compounds with oxalic and nitric acids closely resemble 

 those of urea with the same acids. Although guanidin when boiled with sulphuric 

 acid or baryta water readily yields urea (and simultaneously ammonia) this can in 

 no way be taken as implying a possible formation of urea from proteids directly. 

 Quite recently a crystalline base called ' ly satin,' which readily yields urea when 

 boiled with baryta water 8 , has been isolated from among the products of the decom- 

 position of casein by hydrochloric acid and chloride of zinc. The formula of this 

 base is given as C 6 H n N 3 0, thus placing it in close compositional relationship with 

 kreatin C 4 H 9 N 3 2 and kreatinin C 4 H 7 N 3 0. 



It cannot as yet be said that we possess any real knowledge of the 

 constitution of proteids, and the question will probably remain unsolved 

 until some entirely new departure is made in attacking the problem or 

 until some new property of proteids is discovered by which their 

 absolute purity may be determined as the necessary preliminary to the 

 whole investigation. The so-called crystallised proteids (see above, 



1 For Schutzenberger's most recent attempts to synthetise proteids, see Compt. 

 Rend. T. 112 (1891), p. 198. 



2 Gaz. med. 1879, p. 521. Compt. Rend. T. 93 (1881), p. 771. 



3 Jn. f. prakt. Chem. Bd. xxxi. (1885), S. 129. 



4 Ann. d. Chem. u. Pharm. Bd. C. (1856), S. 247. Compt. Rend. T. LXX., p. 866. 

 T. Lxxm.,p. 1323. 



5 Ibid. T. LXXIII., p. 1219. 



6 See Stadeler, Jn. f. prakt. Chem. Bd. LXXII. (1857), S. 251. Low, Ibid. (N. F.) 

 Bd. in. (1871), S. 180. Tappeiner, Ber. k. Sachs. Gesell. 1871. 



7 Ann. d. Chem. u. Pharm. Bd. 201, (1880), S. 369. 



8 Drechsel, Ber. d. d. Chem. Gesell. Jahrg. xxni. (1890), S. 3096. Cf. Siegfried, 

 Ibid. Jahrg. xxiv. S. 418. 



