46 CHEMICAL CONSTITUENTS OF BODY AND FOOD. 



is quite in accordance with Sabanejeff's l cryoscopic determination of the 

 molecular weights of these substances ; he gives the molecular weight 

 of protoproteose as 2467 to 2640, of deuteroproteose as 3200, and of 

 peptone as 400 or less. The diffusion power of the different sub- 

 stances investigated by Kulme was as follows : Heteroproteose is 

 the least diffusible of the proteoses; in neutral saline solutions it is 

 precipitated as the salt passes out, and none goes through the dialyser ; 

 dissolved in ammonia it loses 5 -2 2 per cent. Deuteroproteose comes 

 next (loss, 241 per cent.) ; then protoproteose (loss, 28*3 per cent.) ; 

 while peptone loses 51 to 51 '8 per cent. Each experiment lasted 

 twenty -four hours. 



Action on polarised light. All the proteids are levorotatory. The 

 specific rotatory power of some of jthe principal members of the group 

 is as follows : 



Colour reactions. These are numerous, and doubtless depend for their 

 occurrence on the various radicles which, as we have seen, are probably 

 present in the proteid molecules. Many of them are given by certain of 

 the decomposition products of the proteids ; and by a careful comparison 

 of these simpler substances, conclusions have been reached concerning the 

 particular groups in the proteid molecule to which each reaction is due. 



The majority of the colour tests are due to the presence of the 

 aromatic radicle ; it will, therefore, be well to preface the description of 

 the reactions themselves by a classification of the aromatic substances 

 derived from proteids by putrefaction. Salkowski 8 arranges them into 

 three groups ; whether all these groups exist pre-f ormed in the proteid 

 molecule, or are derived, as Maly considered, from only one aromatic 

 group, matters but little in the question under investigation. The 

 groups are as follows : 



First group The phenol group. This includes tyrosine, the aromatic 

 hydroxy acids, phenol, and cresol. 



Second group The phenyl group. This includes phenylacetic and 

 phenylpropionic acids. 



1 Ber. d. deutsdi. chem. Gesellsch., Berlin, Bd. xxvi. S. 385. 



2 Ztschr.f. Chem., Leipzig, 1864, S. 737. 



3 Jahresb. ii. d. Fortschr. d. Thier-Clicm., Wiesbaden, Bd. xi. S. 17. 



4 Arch. f. d. ges. PhysioL, Bonn, Bd. xii. S. 378; Chem. Centr.-BL, Leipzig, 1876, 

 S. 295, 811, 824. 



5 Jahrcsl. it. d. Fortschr. d. Thier-Chem., Wiesbaden, Bd. xv. S. 184. 



6 Ztschr.f. physiol. Chem., Strassburg, Bd. xi. S. 508. 



7 Ztschr.f. Biol, Miinchen, Bd. xx. S. 51. 



8 Ztschr.f. physiol. Chem., Strassburg, Bd. xii. S. 215. 



