252 ELIOT R. CLARK AND ELEANOR LINTON CLARK 
they become stationary and send out many fine processes. 
These processes are withdrawn and renewed continuously, 
though tending to become more and more stable. At this stage 
they resemble very closely small connective-tissue cells. They 
are not transformed into connective-tissue cells, however, for 
eventually—probably corresponding to a diminution in the 
intensity of the croton-oil action—the processes are retracted 
and the leucocytes resume amoeboid powers. After the oil has 
been extruded, the leucocytes remain stationary for several days 
in a spherical condition, after which they scatter through the 
tissues. Wandering cells free in the tissue spaces and leucocytes 
which emigrate from the blood-vessels do not differ in their 
reaction. Leucocytes may enter lymphatic vessels and emerge 
again, but we saw no evidence whatever of the origin of leucocytes 
from lymphatic or from blood-vascular endothelium. 
b) Pigmented leucocytes move toward the croton-oil globule 
and are more resistant to its action than the other leucocytes, 
for they may even come in contact with the oil globule without 
showing any diminution in their motility. 
3. Blood capillaries near the globule show thickening and 
vacuolization of the endothelium, and, later, narrowing of the 
lumen, with, in many cases, retraction of endothelium. Extrav- 
asation may occur through the injured part of the wall. 
4. Lymphatic capillaries near the globule also show vacuoli- 
zation of the endothelium, and their lumen may become much 
distended, particularly in case an edema develops. The injured 
capillary may be retracted, but may grow out again later after 
the oil globule has been extruded. 
5. Throughout the inflammatory reaction, each type of cell— 
leucocyte, connective-tissue cell, blood-vessel endothelium, and 
lymphatic endothelium—maintains its specificity, and there is 
no evidence for the transformation of one type of cell into 
another. 
