APR] CHEMICAL BASIS OF THE ANIMAL BODY. 709 



a current of carbonic anhydride, filter, and wash the precipitate with 

 water, alcohol and aether : the complete removal of the fat carried 

 down with the casein presents some difficulties. Magnesic sulphate 

 added to saturation also precipitates casein from milk ; the precipitate 

 as thus formed is readily soluble on the addition of water. 



CLASS III. Globulins. 



Besides the native albumins there are a number of native proteids 

 which differ from the albumins in not being soluble in distilled water; 

 they need for their solution the presence of an appreciable, though it may 

 be a small, quantity of a neutral saline body such as sodic chloride. 

 Thus they resemble the albuminates in not being soluble in distilled 

 water, but differ from them in being soluble in dilute sodic chloride 

 or other neutral saline solutions. Their general characters may be 

 stated as follows. 



They are insoluble in water, soluble in dilute (1 p.c.) solutions of 

 sodic chloride ; they are also soluble in dilute acids and alkalis, being 

 changed on solution into acid- and alkali-albumin respectively unless 

 the acids and alkalis are exceedingly dilute. The saturation with solid 

 sodic chloride of their solutions in dilute sodic chloride, precipitates 

 most members of this class. 



1. Globulin (Crystallin}. 



If the crystalline lens be rubbed up with fine sand, extracted with 

 water and filtered, the filtrate will be found to contain at least three 

 proteids. On passing a current of carbonic anhydride a copious precipi- 

 tate occurs ; this is globulin. 



The addition of dilute acetic acid to the filtrate from the globulin, gives a pre- 

 cipitate of alkali-albumin 1 ; and the filtrate from this if heated gives a further pre- 

 cipitate, due to serum-albumin. 



In its general reactions globulin corresponds almost exactly with 

 the next members of this class (paraglobulin and fibrinogen), but has no 

 power to form or promote the formation of fibrin in fluids containing 

 the above-mentioned bodies, and possesses the following special features. 

 1. According to Lehmann, its oxygenated, neutral solutions become 

 cloudy on heating to 73 C., and are coagulated at 93 C. 2. It is readily 

 precipitated on the addition of alcohol. According to Hoppe-Seyler, it 

 is not precipitated on saturation with sodic chloride, resembling 

 vitellin in this respect. 



1 But see also Pfluger's Arch. Bd. xm. (1876), S. G31. 



