PRINCIPLES OF VETERINARY SURGERY 453 



cording- to Behring an animal has a given amount of natural 

 antitoxin capable of neutralizing a given dose of toxin. If 

 only a certain dose is injected the animal does not take teta- 

 nus. When the dose is large, there is not sufficient anti- 

 toxin to neutralize it and tetanus results. Death super- 

 venes through lack of antitoxin. It might be said in reply to 

 Behring's view that the animal dead from tetanus still has a 

 rich stock of antitoxin, as its brain is still capable of neutral- 

 izing many toxins in vitro, and that the antitoxic supply from 

 the brain and medulla is not measured by the progress of the 

 tetanus. 



Another argument in favor of the "chemical theory" has 

 been invoked ; — the antitetanic serum is preventive and not 

 curative, because it can only neutralize the toxin itself. It 

 is without effect on the new substance, which in reality causes 

 the tetanus. 



These different theories are rather obscure. They are 

 mere hypotheses, and are all open to criticism. They are in- 

 sufficient to explain the pathogenesis of the tetanus spasms. 



ANNOTATION. 



It has also recently been shown by Hektoen that some of the lower ani- 

 mals are immune to tetanus because other cells such as liver cells combine 

 with tetanus toxin and thus prevent its action upon the nervous system. — 

 L. A. M. 



It remains to be explained in what part of the nervous 

 system the tetanic toxin, or the new substance, — the forma- 

 tion of which has been admitted, — acts. The investigations 

 Of Courmont have demonstrated that the tetanic poison has 

 no effect on the muscles. It is not a muscle poison, but acts 

 exclusively on the nervous system. By submitting tetanized 

 animals to the action of curare, which paralyzes the motor 

 nerves and thus separates the muscular system from the 

 motor nervous system, the spasms immediately and entirely 

 disappear. Tetanic toxin is therefore not a muscle poison. 

 Section of motor nerves, or of their medullary roots, renders 



