110 
E. MINK. 
Another important process, closely connected with leucocyte 
migration, is the exudation of liquor sanguinis. This phenomenon 
has long been regarded as a chief characteristic in inflammation. 
It is one of the phenomena which could not easily have been 
overlooked, as without it the pre-eminent symptom of swelling 
could not well be otherwise explained. 
In severe forms of inflammation, red corpuscles also escape 
from the blood-vessels in much smaller number than white; yet 
in some instances sufficiently numerous to give to the effusion a 
hemorrhagic character. 
Since the discovery of emigration of blood leucocytes, it has 
been argued that their escape from the capillaries would be im¬ 
possible, unless these vessels were porous. It has been held that 
this could not be, as injections have been made of so-called sol¬ 
uble prussian blue, without the slightest extravasation taking 
place. 
It would seem that if the porosity of the capillaries is a neces¬ 
sary condition in order to facilitate the passage) of leucocytes, 
then the objection is a valid one. 
But this objection is answered by the fact that the capillary 
is not a dead conduit, but a tube of living protoplasm. And that 
it is not difficult to conceive how the “ membrane may open to 
allow the escape of leucocytes, and close again after they pass 
out.” 
The amorboid movements of blood leucocytes is admitted; 
and it is known that when a mass of protoplasm is separated in 
two parts, and again allowed to come in contact, they close as 
perfectly as if they had not been severed. 
Furthermore, recent histological examinations have shown 
that the capillaries are composed of a “ thin elastic endothelial 
membrane, namely, a single layer of nucleated cell plates. This 
endothelial membrane resembles other membranes in that its 
cells are united one to another by an albuminous intercellular 
cement substance, which latter, in nitrate of silver preparations, 
is seen as dark irregular lines separating the cells.” 
Sanderson says that “ the distension of the capillary vessels, 
which occurs during inflammation to an abnormal degree, is such 
as to cause a separation at many points of the intercellular 
