230 ELIOT R. CLARK AND ELEANOR LINTON CLARK 
ingest it. A week after the production of such an injury, the 
only signs of reaction remaining are a slight irregularity in the 
edge of the fin, the radiation of the processes of near-by con- 
nective-tissue cells toward this defect, and the presence of more 
than the usual number of pigmented leucocytes (fig. 5). 
Fig. 5 Same region one week after the injection of croton oil. The injury 
is almost repaired, only a slight irregularity in the edge of the fin is noticeable, 
toward which the processes of the connective-tissue cells radiate. A slightly 
greater number of wandering cells than in adjoining regions is still present. 
The general picture of a micro-inflammation, illustrated in 
figures 1 to 5, was obtained by watching the same field without 
interruption for twenty-four hours or more after the injection 
of a globule of croton oil. During the succeeding days, the 
region was observed once or twice daily and a record made. In 
other specimens, a certain type of cell or tissue was selected and 
watched intensively during the course of the inflammation. 
These will be described separately. 
