REACTION OF CELLS TO CROTON OIL 224 
Within a few hours after the extrusion of the globule of croton 
oil, the opaque area which had occupied the region of the croton 
oil begins to clear up. The pigmented leucocytes, which had 
crowded in close to the croton oil, now scatter in all directions 
and wander wildly and rapidly through the tissue spaces away 
from the region. After this scattering of the pigmented leu- 
cocytes, the area once occupied by the croton oil, is very thin, 
Fig. 2 Sketch of the same region as in figure 1, begun at 12:30 P.M., May 
30th, showing the wall of leucocytes, with processes, which has formed at a short 
distance from the oil globule. 
and there may even be a hole through the tail at this point 
However, a small opaque clump, consisting of cell debris sur- 
rounded by pigmented leucocytes, remains in the fin and is not 
disposed of for several days. 
During the first twelve hours or more after the extrusion of 
the croton oil the clear leucocytes in this part of the fin remain 
motionless and spherical. During this period new leucocytes 
were seen to come out from the blood-vessels and to approach 
the site of injury. However, when they reached the region 
