THE PRECIPITINS AND THEIR ANTIBODIES 29 1 



These two assumptions regarding m seem the most prob- 

 able. In the first case the constants of reaction are of the 

 same order of magnitude; in the second case K^ is of the 

 same order of magnitude as K^p. As, further, n = 2.45 



TS- -IS" 



-, and - has a positive value, n can only be I or 2 (if we do 



not take into consideration fraction numbers). The proba- 

 bility is therefore that the soluble compound of precipitate 

 with the active fraction of the horse-serum is built up of one 

 molecule of the precipitate and one or two molecules of 

 the other reacting substance. 



In some cases it is not necessary to assume that the 

 precipitate is dissolved on the further addition of the 

 serum which has been injected. A very interesting 

 instance of this behaviour is given by Hamburger in 

 the action of the serum of a rabbit treated with sheep- 

 serum on the sera of three different animals, viz. : sheep, 

 goat, and bullock, which are so closely related to each 

 other that all yield precipitates with the said rabbit-serum. 

 As is natural, the sheep-serum yielded the most voluminous 

 precipitate ; next comes the goat-serum, which animal is 

 the most closely related to the sheep ; and the least quan- 

 tity of precipitate is given by the serum from the bullock, 

 which is less closely related to the sheep than is the goat. 

 The figures are given in the following three tables. The 

 rabbit-serum was always used in the quantity of 0.4 c.c. 



The quantity of the precipitate is given in scale-divisions 

 of the capillary tube (100 divisions = 0.04 c.c.). The sheep- 

 serum was normal serum diluted with 49 times its volume 

 of i per cent solution of sodium chloride. The sera of 

 goat and bullock used in the following two series of ex- 



