140 IMMUNE SERA 



of the pseudo globulin predominate, showing that 

 it is the specific serum which furnishes the greater 

 part of the precipitate. The presence of salts 

 seems to be necessary for the precipitin reaction. 

 A temperature of 37 C. hastens, while a low tem- 

 perature markedly retards the reaction. In either 

 case, the amount of precipitum is uninfluenced. 

 The presence of even small quantities of acids or 

 alkalies markedly reduces the amount of precipitum 

 formed, but an increase of salt (NaCl) has little effect. 



Practical Application. These precipitins have 

 very recently found a practical application. Fish, 

 Ehrlich, Morgenroth, Wassermann, and Schutze 

 investigated the specific action of lactoserum. They 

 found that a serum derived by treating an animal 

 with cows' milk contained a precipitin which reacted 

 only on the casein of cows' milk, but not on that of 

 human milk or goats' milk. The serum of an ani- 

 mal treated with human milk was specific for the 

 casein of human milk, etc. Ehrlich, Morgenroth, 

 and Wassermann also experimented with the serum 

 resulting from treatment with chicken egg albumin, 

 and found that this, while not strictly specific so far 

 as closely related species are concerned, is yet so 

 against other species. The precipitins, therefore, 

 react on closely related albumins, but are specific 

 against those of unrelated species. 



The Uhlenhuth Test for Differentiating Albumins. 

 As a result of his researches Wassermann pro- 



