336 Chapter XI 



blood of fowls that have received an injection of tetanus toxin causes 

 typical tetanus in susceptible animals. This tetanigenic property of 

 the blood persists for a certain number of days. When it is measured 

 by the quantitative method, it is found that all or almost all the 

 tetanus toxin injected into the peritoneal cavity of the fowl passes 

 into the blood and remains there intact for a variable number of days. 

 From a morphological point of view the blood, immediately after the 

 injection of the toxin, exhibits a hyperleucocytosis of greater or less 

 duration. 



When the fowls are killed at the stage when their blood becomes 

 tetanigenic (as the result of the injection of the toxin into the peri- 

 [353] toneal cavity), it can be demonstrated that their viscera are not 

 capable of producing tetanus in susceptible animals except in so far 

 as they contain blood. It is only the vascular organs, rich in blood, 

 such as the spleen, liver, kidneys, thyroid gland and bone-marrow, 

 that impart tetanus and then only in so far as they have not been 

 freed from blood. Of the various organs only the genital glands, 

 ovaries or testes, absorb a certain amount of the injected toxin. Very 

 young testes or the smallest ovarian ova containing as yet no trace of 

 yellow yolk, when injected into mice, produce a fatal tetanus. 



In fowls, insusceptible to tetanus toxin, this toxin is found, 

 then, in the sexual glands and in the blood. When, in order 

 to ascertain the exact localisation of this toxin, we measure the 

 tetanigenic power of the whole blood as compared with that of the 

 aseptic exudations induced by the injection of gluten-casein, and 

 necessarily much richer in leucocytes, we get the result that the ex- 

 udations contain more tetanus toxin than does the blood. We are 

 led, therefore, to the conclusion that this poison is absorbed, at least 

 in part, by the leucocytes, and it is in these elements and in the 

 genital cells that we must look for the factors which arrest the toxin 

 and prevent its reaching the nerve centres. 



Cellular or histogenic immunity is often contrasted with chemical 

 immunity without taking into consideration the real analogies and 

 diiferences to be found between them. It is evident that in both 

 groups the organism of the animal modifies the introduced toxins and 

 that this modification is a chemical process. In cellular immunity, 

 however, this act is preceded by certain biological phenomena, such 

 as the reaction of the formed elements and the absorption of the 

 noxious substance. Immunity in these cases is more complex than in 

 the example where the toxin is neutralised by a direct action of the 



