REACTION OF CELLS TO CROTON OIL 237 
Different types or degrees of reaction of connective-tissue 
cells toward the croton oil were noted. These depended on the 
location of the cells with relation to the globule and on the time 
elapsing after the injection. The first type—mild injury— 
appeared immediately after the injection in cells surrouhding 
the globule. Later, this type persisted in the cells situated 
between the globule and the margin of the fin, in the cells of the 
middle layer located on the outskirts of the ‘granular zone.’ 
In the mild type of injury the processes of the cells become 
shorter, thicker, and more highly refractile and stand out straight 
and stiff (fig. 8 and fig. 10, B). In the case of the cells distal 
to the croton-oil globule, connections between neighboring cells 
are maintained and the shorténing and stiffening of the connecting 
processes may be instrumental in causing the puckering of the 
tail which occurs in this region soon after injection (fig. 8). 
A more severe type of injury begins to appear about twenty 
minutes after the injection in the connective-tissue cells of the 
middle layer situated nearest the globule, and later spreads to 
other more distant cells. It is this type of reaction which gives 
the characteristic granular appearance to the area around the 
globule and especially centrally to it. This type of injury is 
illustrated in figure 9, C, and figure 10, C. The cell processes 
are greatly shortened, the cell body becomes thicker and vacu- 
olated, and the nucleus shows plainly. The vacuoles give the 
cell a honeycombed appearance, and they may be so large and 
numerous as to indent the nucleus. Many of the vacuoles 
contain specks in Brownian movement. This rounding up and 
vacuolization of the connective-tissue cells spreads to the cells 
farther away from and more proximal to the globule, and also 
to the superficial layer of connective-tissue cells in the vicinity 
of the globule. 
The third type of injury may be observed two or three hours 
after the injection in those connective-tissue cells located in close 
proximity to the croton oil. In these cells, one of which is 
shown in figure 10, D, the processes are shortened until the cell, 
in some cases, resembles a round ball. The cell proptolasm is 
practically filled with vacuoles and the outlines are hazy. 
THE AMERICAN JOURNAL OF ANATOMY, VOL. 27, NO. 2 
