IMMUNITY. 



79 



and scorpions, as well as the phylotoxins, such as ricin, abrin, 

 crotin, and robin. 



Immunity, more than any other problem, directly concerns 

 the medical profession and indirectly the international commer- 



Fig. 53. — Hematopinus phalangeB ovis, after Nilos. 

 a. Adult. b. Egg cemented to hair. 



cial welfare. It was a laboratory fad of the pathologists until 

 they demonstrated to the practitioners that it was feasible to 

 produce immunity in man and animals. Veterinarians have now 



Fig. 54. — Pule\ Serratifeps. aftn- Tu'^'-rer 



