INFECTION AND IMMUNITY. 465 



work upon the bactericidal action of the animal econ- 

 omy. In these experiments Nuttall showed positively 

 that the destruction of virulent bacteria in the blood of 

 animals was not necessarily dependent upon the imme- 

 diate presence of living leucocytes, but that the serum 

 of the blood, when quite free from cellular elements, 

 possessed this power to a degree eciual to that of the 

 blood when all the constituent parts were present. In 

 the blood, as such, phagocytosis could be seen, but, as a 

 rule, the bacteria presented evidence of having under- 

 gone degenerative changes before they had been taken 

 up by the wandering cells. 



Contrary to the notions in existence at the time, 

 Traube and Gscheidlen,^ as far back as 1874, demon- 

 strated that considerable quantities of septic material 

 could be injected into the circulating blood without 

 apparently any effect upon the animal. As a result 

 of these experiments, the question that naturally pre- 

 sented itself was : Does the animal organism possess 

 the power of rendering septic organisms inert, and if 

 so, to what extent ? Their further work showed that 

 appreciable numbers of living bacteria could be injected 

 into the circulation of warm-blooded animals without 

 producing any noticeable effect. Particularly was this 

 the case with dogs. If they injected into the circula- 

 tion of a dog as much as 1.5 c.c. of decomposing 

 fluid, the blood drawn from the animal after from 

 twenty-four to forty-eight hours showed no especial 

 tendency to decompose, though it was kept under obser- 

 vation for a long time. They believed this power, of 

 rendering living organisms inert, to be possessed by the 



1 Jahresbericht der Sohleaisclien Ges. fiir Cultur., 1874 ; Jahr. iii. p. 179. 



