IMMUNITY AND SUSCEPTIBILITY 117 



assumes that after the first attack the micro-organisms leave 

 behind them some product of metabolism that is inimical to 

 their existence, and this theory is capable of receiving 

 support from various experimental facts. 



It is on this hypothesis, and the theory of acclimatisation, 

 that the antitoxin treatments which are just now receiving 

 so much attention are based. By antitoxin treatment we 

 endeavour to arm the body against the growth of the specified 

 organisms or the formation of their metabolic products, by 

 putting into it, ready-made, those products that would be 

 produced naturally in convalescence, and by their action 

 would bring the disease to a successful termination. 

 Accounts of the employment of antitoxin treatments are 

 to be seen in every issue of the medical papers, but up to 

 the present date the only diseases which have been exten- 

 sively treated in this way are diphtheria and cholera, in 

 both of which a decided measure of success has been met 

 with. 



Acclimatisation Hypothesis. — According to this hypothesis, 

 it is assumed that the cells of the body become used to the 

 products of the organisms, and that at last they cease to 

 have any injurious influence on them. From analogy this 

 seems a tenable theory, as we see in both the animal and 

 vegetable kingdoms numerous examples of successful accli- 

 matisation. 



The Phagocyte H3rpothesis. — This hypothesis was first 

 put forward by Metschnikoff, who when experimenting with 

 virulent anthrax bacilli on frogs, which are normally insus- 

 ceptible to anthrax, found that the white corpuscles put 

 out two processes to surround the bacilli, which were 

 ultimately absorbed into the centre of the corpuscle. 



He also held that if in the case of a local infection the 

 first number of leucocytes that hurried to the spot were not 

 sufl&cient to repel the invaders, more and more were brought 



