154 LECTURES ON IMMUNITY 



cases where maxima or minima of a certain effect are 

 observed at a certain concentration of the reacting sub- 

 stance. One of the most startling of these phenomena is 

 observed on injection of a mixture of the botulismus-poison 

 produced by Bacillus botulinus, and its antibody, obtained 

 from the blood-serum of animals that have been injected 

 with this poison. Madsen used, for instance, a mixture of 

 o.i c.c. with 0.0013 c.c. of its antitoxin. The injection of 

 ten such doses in a guinea-pig (of 250 g. weight) had 

 no effect; two doses gave just a trace of illness charac- 

 terised by a peculiar flaccidity of the animal; one dose 

 caused a flaccidity lasting four to seven days. Injections 

 of between 0.013 and 0.5 doses had a lethal effect, and the 

 maximal toxicity was shown by a o.i dose, the animal dying 

 after only two days ; o.oi dose was no longer lethal, but 

 caused flaccidity lasting seven days ; and 0.003 dose only a 

 trace of flaccidity lasting only one day. 



Another similar instance with a minimum and a maxi- 

 mum of effect is shown in haemolysis by means of sapo- 

 nin (Madsen and Walbum), an extract from the roots of 

 Saponaria; 8 c.c. of a suspension of I per cent of erythro- 

 cytes from horse blood was added to the following quanti- 

 ties of a 0.02 per cent solution of saponin with water up to 

 a total quantity of 10 c.c. This mixture was placed for three 

 hours at 37 C. and thereafter cooled on ice and the de- 

 gree of haemolysis in per cent measured on the following 

 day after the unattached erythrocytes had subsided. 



Quantity of saponin in c.c. = I 0.7 0.5 0.4 0.3 0.25 0.2 0.17 O 

 Haemolysis in per cent = 35 16 18 30 36 36 45 41 o 



Similar observations were also made with mixtures of sa- 



