278 LECTURES ON IMMUNITY 



that animals generally produce antibodies against different 

 toxins and that this production is only augmented by the 

 experimental injection of toxins into the blood of the ani- 

 mal. In other words, the antibodies in normal sera ought 

 to be identical with those produced after active immunisa- 

 tion. This is evidently not true for the antirennets. There 

 are also many other considerations which speak against 

 Ehrlich's idea, of which Bashford has given a detailed 

 criticism. 1 



In one point I cannot agree with Bashford. He assumes 

 that the toxin, i.e. in this case the rennet, is divided between 

 the normal serum and the rest of the fluid. This is quite 

 like the idea held by Biltz. According to Bashford, if for 

 the second serum 0.3 c.c. of the serum takes half of the 

 rennet, then 0.6 c.c. ought to fix two-thirds of it, whereas 

 it actually takes 78 per cent; 0.9 c.c. should fix 75 per cent, 

 whereas the table gives 88; 1.2 c.c. should carry 80 per 

 cent, instead of the 91 per cent observed. 



This last series may be calculated according to the 

 scheme of Biltz; it gives a nearly constant value of the 

 exponent /, viz. / = 2.3 (cf. p. 216). But the first series 

 for normal horse-serum yields a steadily increasing value 

 of/ with increasing n. Between n = o.i and n 0.4, / is 

 0.85 ; between n 0.4 and n i.o, we find / = 1.5 ; be- 

 tween n = i.o and n = 1.5, / is 2.4; for higher values of 

 n, p is found to be 3.3. 



If we apply the idea of Biltz to the fixation of rennet 

 to antirennet, we find that at first the concentration oil 

 rennet in the serum is constant until about n 0.6, whereas 

 that of the rennet in the fluid sinks in the proportion 6 to i 



1 Bashford: Journ. of Pathology, 8. 62 (1902). 



