230 MICROBES AND TOXINS 



the cerebral cortex (and the grey matter of the spinal cord) of 

 mammals only ; in fowls immunised against tetanus the brain 

 has much less neutralising power than the blood, the liver, or 

 the kidney. The brain of the frog does not neutralise the 

 toxin, although under certain conditions the frog is susceptible 

 to tetanus. 



Cholesterin, lecithin, and even olive oil and carmine (a 

 substance derived from the fatty body of the cochineal insect) 

 are capable of neutralizing a certain quantity of toxin ; now 

 the brain substance contains both cholesterin and lecithin. 

 It is, however, another lipoid in the brain, protagon, which 

 chiefly fixes the toxin and perhaps permits of its transport 

 along the nerves (Landsteiner and Botteri.) A. Marie and 

 Tiffeneau have recently insisted that in Wassermann's experi- 

 ment it is not a destruction which takes place, but a combina- 

 tion from which the toxin may be recovered. Anyhow, the 

 neutralization by the cerebral tissue is a phenomenon of 

 molecular adhesion, analogous to a dyeing process. 



By injecting the tetanus toxin directly into the brain it has 

 been shown that this very brain substance which, ground up 

 in a glass, neutralizes the toxin, does not neutralize in the 

 living animal the most minute dose. It is therefore impossible 

 to suppose that the brain is a source of antitoxin (Roux and 

 Borrel). 



An immunized rabbit, rendered resistant to toxin by subcu- 

 taneous inoculation, succumbs when the toxin is injected into 

 the brain : the antitoxic action is therefore due to cells lying 

 between the periphery and the centre ; the poison is neutralized 

 en route. 



What are these cells? We find that sublethal doses of 

 tetanus toxin produce in the fowl a great afflux of leucocytes 

 into the blood ; further, in a fowl injected with tetanus toxin, 

 far less toxin is to be found in the blood than in (aseptic) 

 exudates rich in leucocytes. Metchnikoff therefore considers 

 that the protection of the body against toxins also depends on 

 the leucocytes. 



The rabbit can stand large doses of atropin injected subcu- 



