IMMUNITY 231 



taneously or into the circulation, but it is very susceptible 

 to intracerebral injection ; is it the leucocytes which dispose 

 of the poison when injected into the veins ? This is possible, 

 for the poison can be recovered from the leucocytes after it 

 has disappeared or is only to be found in traces in the blood 

 plasma (Calmette). 



When guinea-pigs are injected intraperitoneally with arsenic 

 trisulphide, a salt which is only slightly soluble, the particles 

 are taken up by the macrophages. When a soluble salt like 

 potassium arsenite is injected, when the animal recovers it is 

 in the leucocytes that the arsenic is found on chemical analysis 

 (Besredka). The phagocytes also absorb lead salts (Carles). 

 The white corpuscles of the blood are thus equally capable of 

 resisting mineral as microbial poisons. 



When a guinea-pig is inoculated with the mixture of 

 mammalian brain ground up with tetanus toxin the solid 

 particles attract the phagocytes which seize them and with 

 them the attached toxin. If the toxin is injected along with 

 particles to which it does not attach itself (e.g. the mixture of 

 toxin + frog's brain) it can diffuse, and the leucocytes no 

 longer protect the animal. 



After the discovery of the antitoxins one was apt to think 

 that in every infection there was an intoxication and that the 

 neutralization of the poisons ought to precede phagocytosis 

 which is only a secondary phenomenon. But experience has 

 shown that the phagocytes can also digest the microbial toxins. 



Certain bacteria secrete substances which weaken and 

 destroy the phagocytes ; among these antiphagocytic microbial 

 poisons may be classed the agresstns of Bail. Now the 

 phagocytes are capable of absorbing and digesting these 

 substances without any outside assistance. 



Certain bacterial extracts prepared outside the body and 

 injected in sufficient quantity are prejudicial to phagocytosis. 

 Yet the same bacteria which furnish these extracts are 

 absorbed by the leucocytes when these latter have their 

 activity reinforced. 



When dead typhoid bacilli are injected into the peritoneum 



