DESCRIPTION OF PLATES. 165 
mation is produced by any cause, they do so in 
large numbers. Quite recently, the writer had the 
opportunity of seeing white blood-corpuscles in 
active amoeboid movement, which had escaped 
from the capillary blood-vessels of an inflamed 
mucous membrane some hours previously. They 
were in urine, and had found their way into this 
fluid from the inflamed mucous membrane of the 
bladder. Under these circumstances, they pass 
under the name of pus-corpuscles ; but their iden- 
tity with the white corpuscles of the blood can 
scarcely be questioned, 
If white blood-corpuscles or pus-corpuscles are 
spread upon a thin glass cover and allowed to dry, 
and are then treated with a suitable staining re- 
agent, — such as methyl-violet, —it will be found 
that they are not homogeneous bits of protoplasm, 
but that they contain one or more deeply colored 
masses, called nuclei. 
The white corpuscles are far more uniform in 
size than the red in different species of vertebrate 
animals, and do not vary greatly from 35/55 of an 
inch in the Mammalia. 
The continued vitality of white blood-corpus- 
cles and of ciliated epithelium cells after removal 
from the body of the animal in which they had 
their origin, is a striking phenomenon, because 
their spontaneous movements give evidence of 
this vitality; but there is no reason to suppose 
that these are exceptional cases. Indeed we 
have evidence that the vitality of detached tissues 
and even of organs may be preserved for a consid- 
