



CHAP. I.] THE PROTEIDS. 17 



(2) Egg-albumin. Specific rotation (a),, = -35 -5. Precipitated 

 from its solutions when these are agitated with ether. 



CLASS II. Peptones: proteid bodies exceedingly soluble in water. 

 Solutions not coagulated by heat; not precipitated by sodium chloride, 

 nor by acids or alkalies. Precipitated by a large excess of absolute 

 alcohol and by tannic acid. In the presence of much caustic potash 

 or soda, a trace of solution of copper sulphate produces a beautiful 

 rose colour. 



CLASS III. Globulins : proteid substances which are insoluble 

 in pure water, but soluble in dilute .solutions of sodium chloride; 

 their solutions are coagulated by heat; they are soluble in very dilute 

 hydrochloric acid, being converted into acid-albumins they are 

 also readily converted by alkalies into alkali-albumins. 



(1) Vitellin, not precipitated from its solutions when these are 

 saturated with common salt. Solutions coagulate at 70 75 C. 



(2) Myosin, precipitated from its solutions in weak common 

 salt when these are saturated with sodium chloride. Solutions 

 coagulate at 55 60 C. Solutions in common salt not coagulated 

 by solution of fibrin-ferment. 



(3) Fibrinogen, soluble in weak solutions of sodium chloride. 

 Precipitated from them completely by the addition of sodium chloride, 

 when this amounts to 12 or 16 per cent. Solutions coagulate on the 

 addition of fibrin ferment. Temperature of coagulation 56 C. 



(4) Paraglobulin, soluble in weak solutions of sodium chloride. 

 From very weakly alkaline solutions paraglobulin is precipitated by 

 the addition of a very small quantity of common salt ; a further ad- 

 dition of this body leads to re-solution of the precipitate, which is 

 thrown down again when the amount of sodium chloride in solution 

 exceeds 20 p.c. -The precipitation of paraglobulin by sodium chloride 

 is never complete. Paraglobulin is completely precipitated when its 

 solutions are saturated with magnesium sulphate. Solutions not 

 coagulated by addition of fibrin-ferment. Temperature of coagulation 

 varies (according to amount of salts present and mode of heating) 

 between 68 80 C.; on-an average 75 C. 



CLASS IY. Derived Albumins 1 : proteid bodies insoluble in pure water 

 and iu solutions of common salt, but readily soluble in dilute hydrochloric 

 acid and in dilute alkalies. Solutions not coagulated by heat. 



(1) Acid-albumins : obtained by the action of dilute acids (preferably 

 dilute hydrochloric acid) upon solutions of proteids, by action of strong 

 acids upon the solid proteids, and as first products in the action of gastric 

 juice upon proteids. On neutralizing solutions of acid-albumins, they are 

 precipitated even in the presence of alkaline phosphates. NaCl, added to 

 saturation, also precipitates them. 



(2) a. Alkali-albumins or alkaline albuminates : obtained by the 

 action of dilute alkalies upon the proteids. Possess the properties of sub- 

 class 1, with the exception that in the presence of alkaline phosphates 



rapidity of heating, the coagulation temperature varies, according to Hammarsten, 

 between 68 and 80. , . , 



1 This convenient designation I borrow from Dr Michael Foster. See Text-book of 

 Physiology, Appendix. 



o. : 2 



