BY JAMES M. PETRIE. 119 



The trichloracetic acid figure is less than that for tannic 

 acid. Most proteoses and peptones are soluble in this reagent. 

 Distinct evidence of proteoses is given in Table iv., by the 

 deposit formed on cooling the hot filtrate ; this deposit redis- 

 solves on heating. Proteoses are only partially precipitated 

 by excess, dissolve on boiling, and re-appear on cooling, 

 while peptones are not precipitated.* 



The protein coagulated by boiling the salt extract, slightly 

 acidulated with acetic acid, is , considerably less than the 

 tannin-precipitate. The results of Osborne, Chittenden and 

 Mendel t, show that coagulation of reserve-proteins -.'f 

 seeds is always incomplete, and that their behaviour is 

 wholly diffei-ent from that of animal-proteins. On thi.^ 

 account we cannot designate the uncoagulable protein, which 

 is precipitated by tannic acid, as proteose and peptones, 

 which is so often done in the separation of animal-proteins. 



Carbon dioxide precipitates a little over one-half (63%) 

 the amount obtained by tannic acid. This probably represents 

 the actual globulins present. 



A very small quantity only is obtained by complete satura- 

 tion with sodium chloride. 



By fractional salting out with ammonium sulphate, pre- 

 cipitation begins with six-tenth's saturation. The globulins, 

 which are most readily salted out, appear first ; and since we 

 have seen that carbon dioxide shows the presence of at least 

 63% of globulins, they must constitute the whole of the 

 seven-tenth's fraction, and part of the eight-tenth's. All 

 the work done on the globulins, up to within a few years 

 ago, was based on the fact that globulins were defined as 

 those proteins which could be salted out by half-saturation 

 with ammonium sulphate — a definition very far removed 

 from the trvith, and according to which the extract would 

 contain no globulins at all. 



Martin, C. J., Journ. Physiol. 15, 1894, 375. 

 t Jourii. Physiol. 17, lS9t, 48. 



