188 JOHN STEPHENS LATTA 



of eosinophiles must be considered negligible; the main sources 

 being by the heteroplastic differentiation of lymphocytes and 

 from the blood stream. 



The conditions causing or related to the phenomenon of granu- 

 lopoiesis have not as yet been clearly brought out. The close 

 association of granulopoietic foci with the blood vessels, which can 

 usually be seen, indicates the probability that the blood in some 

 way plays an active part in the formation of the eosinophiles. 

 It is noted also that when parasites (as Coccidia) are present in 

 any abundance that eosinophiles tend to become very numerous, 

 especially in the tunica propria in the immediate vicinity of the 

 parasites. The Coccidia may be found in groups near the bases 

 of the villi, either imbedded in the tunica propria, just under the 

 lining epithelium, in among the epithelial cells, or in the intestinal 

 lumen, just outside the epithelium. The eosinophiles being 

 formed locally or migrating from the blood vessels may invade the 

 epithelium, or in case the parasites are found in the intestinal 

 lumen, may break through the epithelium into the lumen where 

 they gather about the parasites. The eosinophiles often invade 

 the epithelium in such numbers that it is entirely broken up and 

 loses its identity as such. The eosinophiles of both types always 

 gather about and in the midst of the groups of Coccidia in an 

 apparent effort to destroy them or combat their influence. 



Other inflammatory or irritating conditions other than the 

 presence of parasites may also be associated with extensive de- 

 velopment of granulocytes. The fact that eosinophiles are more 

 abundant in the appendix and caecum than in other parts of the 

 intestinal tract may possibly be accounted for by the irritation 

 caused by the presence of fecal matter in the intestinal lumen. 



There is, therefore, surely some relationship existing between 

 the presence of irritating substances, pathogenic organisms, etc., 

 and the production of eosinophile cells. It is well known that 

 eosinophiles from the blood collect in and about places of inflam- 

 mation, but, in addition to that, inflammation or irritation of some 

 kinds in the intestine seems to initiate granulopoiesis locally or 

 the production of connective tissue eosinophiles. The more ex- 



