332 Chapter XI 



pronounced natural immunity against tetanus. They show an un- 

 limited resistance to enormous doses of tetanus poison, and this at 

 low, medium, or high temperatures (30°— 37° C). Green lizards with- 

 stand considerable doses of tetanus toxin. Although they do not 

 contract tetanus, they get rid of the poison exceedingly slowly. Thus, 

 a lizard kept at a temperature of 20° C, and injected with an amount 

 of toxin sufficient to kill 500 mice, at the end of two months still 

 retains in its blood such an amount of the poison that one-tenth of a 

 c.c. will cause fatal tetanus in a mouse. Turtles present an analogous 

 case. The marsh turtle, Emys orbicularis, tolerates very large 

 amounts of tetanus toxin, injected subcutaneously, and this at both 

 low and high temperatures, at 30° C. and beyond (36° — 37"" C). The 

 toxin passes quickly into the blood and remains localised there for a 

 very long time. In a turtle kept in an aquarium at the laboratory 

 the blood was tetanigenic for the mouse even four months after an 

 intra-peritoneal injection of the toxin. In another turtle which lived 

 at incubator temperature (36° — 37° C), the blood was still toxic two 

 months after a subcutaneous injection of tetanus toxin in quantity 

 fatal for 500 mice. In turtles kept at 36° C. I observed abundant 

 transudations into the peritoneal cavity, and the fluid, very poor in 

 [349] formed elements, was found to be very tetanigenic. It must be 

 accepted, therefore, that the toxin is retained in the blood plasma 

 with which it passes into the transudation. Every kind of cell must 

 exhibit a very marked negative chemiotaxis against tetanus toxin for 

 this poison to be retained so long in the body fluids. Under these 

 conditions it is not surprising that in turtles I was never able to 

 observe the slightest antitoxic power in the blood. Their great 

 natural immunity must be due to some other factor. 



The alligator {Alligator mississippiensis) has also been found to 

 be quite refractory to tetanus both at low and at high temperatures. 

 Outwardly alligators behave exactly as do turtles, that is to say, after 

 the injection of various and sometimes very large doses of toxin they 

 exhibit no morbid symptom either general or tetanic. But the par- 

 ticular changes which occur in their organism differ essentially from 

 those met with in the turtle. The toxin is rapidly eliminated from 

 the blood of the alligator, even when it is kept at a relatively low 

 temperature (20° C). Under these conditions of temperature, hoAv- 

 ever, the blood does not become antitoxic although it has lost its 

 tetanigenic property. When, however, the alligators are kept at a 

 higher temperature (32° — 37° C), antitoxic power is developed in 



