234 CLINICAL BACTERIOLOGY. 



of the culture mentioned being required to cause tetanus in 

 an animal weighing about 1000 grams, with death after the 

 lapse of several days. The dog may be looked upon as 

 being naturally immune to tetanus, being affected only on in- 

 oculation with large doses of toxin : from 5 to 10 cu. cm. and 

 more. Birds are highly immune, withstanding inoculations 

 of from 10 to 20 cu. cm. of highly toxic tetanus-bouillon ; 

 still larger amounts of toxin, naturally, give rise to fatal 

 tetanus both in the hen and in the pigeon. Frogs also 

 may suffer from tetanus if after inoculation they are kept 

 permanently in a heated room ; but relatively large doses 

 of toxin are necessary, and the disease develops only after 

 two or three weeks. 



Introduction of the tetanus-virus into a wound or injec- 

 tion into the large cavities of the body or directly into the 

 veins acts in the same way as subcutaneous inoculation. 

 Experimental infection can not be induced by way of the 

 digestive or the respiratory tract. 



The period of incubation varies in accordance with the 

 susceptibility of the animal and the virulence and amount 

 of toxin inoculated : between one and two days, in the 

 mouse ; and between eight and fourteen days, in the rabbit. 



Tetanus in animals manifests itself in the form of extensor 

 spasm, which gives rise to a clinical picture entirely analo- 

 gous to that exhibited by tetanus in human -beings. The 

 spasm appears first in the neighborhood of the site of inocu- 

 lation ; thus, when the root of the tail is inoculated, in the 

 hind extremities and also in the tail ; when the nape of the 

 neck is inoculated, in the fore extremities and the muscles 

 of the neck. In the further development of the disease the 

 entire muscular system is involved in the spasm, which 

 quickly leads to death. After intraperitoneal and intra- 

 venous inoculation the spasm is general from the outset. 

 The longer the period of incubation, the slower generally 

 is the course of the disease, and the shorter the period of 

 incubation, the more unfavorable is the prognosis. After the 

 disease has existed for some time recovery not rarely takes 

 place. This ensues always but slowly, the rigid extremities 

 relaxing in the course of weeks or months. On postmortem 

 examination, only slight changes are found at the site of in- 

 oculation when a pure culture has been employed in the 

 inoculation viz., slight infiltration or hemorrhage, and 

 nothing else. If the inoculation has induced no extensive 



