BACILLUS TETANI 463 



bility to tetanus toxin. Human beings and horses are probably the most 

 susceptible species in proportion to their body weight. The common 

 domestic fowls are extremely resistant. Calculated for grams of body 

 weight, the horse is twelve times as susceptible as the mouse, the guinea- 

 pig six times as susceptible as the moyse. The hen, on the other hand, 

 is 200,000 times more resistant than the mouse. 



After the inoculation of an animal with tetanus toxin there is always 

 a definite period of incubation before the toxic spasms set in. This 

 per;' id may be shortened by increase of the dose, but never entirely 

 eliminated.^ When the toxin is injected subcutaneously, spasms begin 

 first in the muscles nearest the point of inoculation. Intravenous 

 inoculation,^ on the other hand, usually results in general tetanus of 

 all the muscles. The feeding of toxin does not produce disease, the 

 poison being passed through the bowel unaltered. 



The harmful action of tetanus toxin is generally attributed to its 

 affinity for the central nervous system. Wassermann and Takaki ' 

 show that tetanus toxin was fully neutralized when mixed with brain 

 substance. Other organs — liver and spleen, for instance — showed no such 

 neutralizing power. The central origin of the tetanic contractions was 

 made very evident by the work of Gumprecht,* who succeeded in stop- 

 ping the spasms in a given region by division of the supplying motor 

 nerves. 



The manner in which the toxin reaches the central nervous system 

 has been extensively investigated, chiefly by Meyer and Ransom, and 

 Marie and Morax. Meyer and Ransom * from a series of careful experi- 

 ments reached the conclusion that the toxin is conducted to the nerve 

 centers along the paths of the motor nerves. Injected into the circu- 

 lation,* the toxin reaches simultaneously all the motor nerve endings, 

 producing general tetanus. In this case too, therefore, the poison from 

 the blood can not pass directly into the central nervous system, but 

 must follow the route of nerve tracts. 



These observations have been of great practical value in that they 

 pointed to the desirabihty of the injection of tetanus antitoxin directly 

 into the nerves and the central nervous system in active cases. 



' Courmont et Doyen, Arch, de phys., 1893. 



' Ransom, Deut. med. Woch., 1893. 



' Wassermann und Takaki, Berl. klin. Woch., 1898. 



* Gunprecht, Pfltiger's Arch., 1895. 



' Meyer und Ransom, Arch. f. exp. Pharm. u. Path., xlix. 



' Marie et Morax, Ann. (}e I'Jnst. Pasteur, 1902. 



