THE PRECIPITINS AND THEIR ANTIBODIES 281 



For the calculation the formula used was that employed 

 before for the calculation of the influence of horse-serum 

 on rennet. Of the solution of hirudin i c.c. is equivalent 

 to the fixed quantity (0.4 c.c.) of the extract, and the con- 

 stant is K = 0.09. The agreement is very satisfying. 

 It therefore seems quite proper to assume that the action 

 of hirudin on the coagulation of blood-plasma is of the 

 same nature as the action of pseudo-globulin on the co- 

 agulation of casein. 



The circumstance that the substances concerned in bio- 

 chemistry react not only with their specific antibodies, but 

 also with other compounds, specially with such well-known 

 properties as acids, bases, salts, or even lecithin and 

 cholesterin, is a very promising feature. For if there 

 were no reactions except with the specific antibodies, which 

 we have very little hope of obtaining in the pure state 

 adapted to a detailed investigation, we would have very 

 slight prospects of rapid progress. 



Besides the coagulating ferments there is another group 

 of precipitins which deserve this name to a higher degree, 

 namely, those prepared by injection into living animals of 

 fluids containing proteins. Among these the lacto-serum, 

 which is obtained by the injection of milk into animals, has 

 been investigated very thoroughly by P. T. Miiller. 1 Other 

 precipitins produced by the intraperitoneal injection of 

 egg-albumen or normal horse-serum into rabbits were 

 studied by Eisenberg; 2 they behaved very like the lacto- 

 serum prepared by the intraperitoneal injection into rabbits 

 and studied by Miiller. 



J P. T. Miiller: Archiv f. Hygiene, 44. 126 (1902); Centralbl f. Bah- 

 teriologie, etc., 32. 521 (1902), and 34. 48 (1903). 



2 Eisenberg: Bull, de VAc. des Sciences de Cracovic, p. 289 (1902). 



