Natural Infection, Susceptibility. 445 



a degree that colonies are formed wMcli produce sufficient toxins 

 to cause intoxication (Teyssandier observed several cases of 

 tetanus following colic). Infection occurs more readily by way 

 of inflamed mucous membranes (Thalmann) and this might 

 explain the occurrence of the disease in dogs after eating spoiled 

 meat (Alessandrini). The tetanus bacilli after passing through 

 the intestinal mucosa may also find a favorable medium for 

 development in exudates or necrotic areas of an internal organ, 

 for example in abscess of the liver (Keleti). Recent experi- 

 ments have also shown that tetanus spores may probably pass 

 in, healthy animals from the intestinal canal to the lymphatic 

 circulation and remain latent in the internal organs, until a 

 time when circumstances favoring their development arise. 



Susceptibility. Among the domestic animals solipeds are 

 most commonly affected by tetanus; the disease occurs much 

 less frequently in cattle, sheep and goats, while hogs and dogs 

 are only occasionally attacked (in dogs the disease occurs 

 usually after extensive and contaminated destruction of tissue, 

 more rarely after docking the tail). Cows are attacked in the 

 majority of instances after labor, only exceptionally following 

 a traumatic gastritis (Friedrich), calves after castration, while 

 in sheep castration, pox inoculation, ear marking, etc., are the 

 leading factors in the occurrence of infection. Among goats 

 the disease was observed almost exclusively in rams which 

 were castrated at an advanced age. 



Young animals are more susceptible than older ones, and 

 the disease may become enzootic among lambs particularly, 

 sometimes also among foals, as the result of infection of the 

 umbilicus (tetanus neonatorum). 



Pathogenesis. Healthy animal tissue is not a good medium 

 for the propagation of the tetanus bacteria. Toxin-free spores, 

 when not inoculated subcutaneously and in excessive numbers 

 (in guinea pigs 2,500 spores according to Vaillard, Vincent & 

 Rouget), are ineffective, as they are engulfed by phagocytes 

 and immobilized. On the other hand toxic spores produce the 

 disease even in very small quantity, as the phagocytes are kept 

 away from them by the negative chemotaxis of "the toxins, and 

 these germinate under the protection of the toxins and enable 

 the bacilli to multiply. In the same manner spores are pro- 

 tected by the simultaneous injection of negatively chemotactic 

 lactic acid or trimethylamin (according to Hektoen this is not 

 the result of chemotactic but antiopsonic actions). This explains 

 the effectiveness of the toxin-containing older cultures as com- 

 pared with the harmless, toxin-free, young cultures. 



When the spores enter necrotic tissue or extravasated 

 blood they multiply rapidly and produce toxins. By injection 

 of spores into such dead tissues (badly contused muscles, blood 

 extravasations) the disease may positively be produced, and 



