518 The American Naturalist. [June, 
as possible. Taking a bit of infected tissue from an animal suf- 
fering from this disease, Metschnikoff placed it under the skin of 
a mammal, such as a mouse or rabbit, and on taking it out and 
examining it, in the course of a few hours, he found that it had 
been surrounded by the wandering cells of the animal, and that 
many of the bacilli had been taken up, and appeared to be under- 
going a process of digestion in their interior (Fig. 3). Of course, 
it often happens that in animals suffering from this disease, the 
bacilli may become so numerous as to kill the amceboid cells, 
and finally cause the death of the animal itself. 
Itis well known that in typhus fever there 
are certain stages of the disease in which great 
numbers of spirilla—another form of bacteria 
—are found in the blood of the suffering 
individual. Now one would naturally expect, 
from what has been stated, that the white 
blood corpuscles would be found to contain 
them ; but, curiously enough, this is seldom, 
if ever, found to be the case. In making ex- 
Fig-3 perimental investigations with the prevention 
Pao x ot from a frog s, of this disease in view, Metschnikoff recog- 
splenitis. After Metschni- Nized in this fact a serious objection to the 
theory which he had advanced concerning 
these leucocytes. He inoculated an ape with the spirilla, and they 
soon appeared in the blood. Some time afterward, however, they 
became less numerous, and finally disappeared altogether. This 
circumstance led Metschnikoff to suspect that perhaps they had 
collected in some other part of the body, so he killed the ape 
and finally found that the amceboid cells of the spleen were filled 
with the missing spirilla. To be sure, some were yet free, but a 
great many were not only invested, but in all stages of digestion. 
This fact throws some light on the unknown function of the 
spleen, and at least indicates the conclusion that it attains to the 
importance of a therapeutic organ. 
In erysipelas there is not only an acute inflammation, but 
also a degeneration of tissues; and it has been for some time an 
unexplained fact that a resorption of these broken-down parts 
