406 ANTHRAX 



the fact that they fail to stain by Gram's method. This change 

 is brought about very quickly by a suitable serum, the change 

 being often complete in ten minutes at 37 C. 



There have been numerous attempts to explain the apparent 

 anomalies of the reaction in question. Bail found that dog serum 

 (normally a good culture medium for the anthrax bacillus) 

 becomes highly bactericidal after the addition of a small amount 

 of rabbit serum, even when this is only present in amount so 

 small that it is devoid of bactericidal action per se. This appears 

 to be due to the presence of immune body in the dog's blood, but 

 no complement. If the action of the rabbit's serum is due to the 

 presence of complement, this must be thermostable, for the effect 

 is not annulled by heating to 50 C. Bail and Petterson found 

 that many other sera could be reactivated with rabbit serum 

 (man, ox, calf, pig, etc.), and that extracts of leucocytes or of 

 organs (liver, bone-marrow) might be equally effective. Malvoz 

 also investigated the presence of immune body by means of the 

 Bordet-Gengou reaction (absorption of complement), and found 

 that the amount in the serum was some index as to the degree of 

 immunity. Thus the blood of the ox and guinea-pig contain 

 none, as is the case with the newly-born puppy, an animal 

 susceptible to anthrax, whereas the adult dog contains a large 

 amount. Remy has also studied the question of the reactivation 

 of sera of various species by complements from others, and 

 notably that of the fowl. Thus the serum of the white rat (an 

 immune animal) contains an immune body, for after heating to 

 55 C. it can be reactivated with fowl serum. On the other hand, 

 the serum of the goat after heating cannot be rendered bacteri- 

 cidal in this way. He holds that there is an absolute concordance 

 between the bactericidal power of the blood, the presence of 

 immune body, and the resistance of the animal to infection with 

 this organism. 



Sobernheim and others have explained the susceptibility of the 

 rabbit by supposing that the immune body has a greater affinity 

 for the cells of the animal than for the anthrax bacillus, and is 

 thus absorbed and rendered useless. 



On the other hand, Metchnikoff holds that the immunity is 

 entirely due to phagocytosis, and finds that the extent to which 

 the bacteria are taken up by the leucocytes is proportional to the 

 degree of resisting power. Anthrax bacilli (and especially the 

 second vaccine, which forms a very good emulsion) are very 



