PRINCIPLES OP VETERtNARY SURGERY 449 



there is always toxin in the blood at the time of the appear- 

 ance of the first symptoms, but this toxin always disappears 

 after some days of tetanus. The frog still \Wes, suffering 

 from intense tetanus after the disappearance of the toxin, 

 and its nerve centers are always scantily supplied with the 

 poison. In the hen tetanic toxin subsists for a long time 

 without modifications. It is not eliminated but transformed. 

 From these experimental investigations it is evident that 

 tetanus does not act alike on all animals. It is important 

 to remember that in the rabbit the toxin has disappeared 

 from the blood and emulsions of the organs, a long time be- 

 fore the disease begins; that certain refractory or slightly 

 sensitive animals like the frog, turtle and chicken may pre- 

 serve the toxin intact for a long time, and that warm frog 

 may become tetanized without having any toxin in the nerve 

 centers. 



The mode of action of tetanic toxin has been very dif- 

 ferently interpreted. Some have claimed that it does not un- 

 dergo any modifications in the organism, but that it diffuses 

 1)y degrees and becomes fixed in the cells of the nerve cen- 

 ters. This hypothesis rests upon the following fundamental 

 experiments of Wasserman and Takaki. The normal brain 

 of a cavy is pulverized in ten cubic centimeters of salt water. 

 A cubic centimeter of this emulsion mixed with tetanus toxin 

 neutralized ten fatal doses, and attenuated sixty fatal doses 

 for mice. It is therefore evident that the brain substance 

 has rendered the toxin harmless. The brain of the rabbit, 

 the pigeon, the horse and man, exhibit the same properties. 

 The brain medulla, or other parts of the body, in lieu of 

 brain substances for this experiment, do not attenuate the 

 toxin. 



These statements have been verified by dififerent authors. 

 Metchnikofif and Conrmont have established that the anti- 

 tetanic property is the privilege of the nerve centers in mam- 



