478 J. A. BADERTSCHER 



thymus was removed. In late developmental stages, there- 

 fore, only the eosinophile cells in the interlobular septa will be 

 considered. The septa of the thymus in embryos from 65 to 

 85 mm. in length contain only a few eosinophile cells. In some 

 sections none were found. In the 100 mm. stage they can be 

 found without much searching while in the 110 mm. stage a 

 single group was found in the sections prepared from the thymus 

 head while those lying singly are more numerous than in the 

 previous stage. In a 125 mm. embryo groups of eosinophile 

 cells are of frequent occurrence and lie usually along the course 

 of blood vessels but some are also present in the deep looser por- 

 tions of the septa. They are also found lying singly in the 

 septa. The greatest numbers occur in stages 165 and 180 mm. 

 long. In the former stage they were more numerous in the 

 superficial thymus than in the thymus head or cervical segment, 

 and on the whole more numerous than in the latter stage in which 

 their distribution was about equal in the different segments 

 examined. In the full term fetus (270 mm.) they are much 

 less numerous in the septa than in the 180 mm. stage. In the 

 last three stages many eosinophile cells are found lying singly 

 in the deep looser portions of the septa but the large majority 

 are found in groups which almost without exception are found 

 in the immediate vicinity of the larger blood vessels where the 

 structure of the septa is comparatively loose. Some groups 

 extend entirely around blood vessels (fig. 8, Eo.C.) while 

 others lie only to one side of them. In some groups the eosino- 

 phile cells he closely together while in others they are more 

 loosely arranged. Without exception a greater or less number 

 of large and medium-sized lymphocytes are promiscuously 

 scattered among the eosinophile cells. 



The eosinophile cells vary in size from very large to medium- 

 sized lymphocytes. The outline of the greater number is spheri- 

 cal but when they lie closely together or in close contact with 

 other cellular elements they may have an irregular shape. The 

 eosinophile granules are coarse, round, and of a nearly uniform 

 size. Their number varies greatly in different cells. In some 

 a few granules may be found in a group to one side of the nucleus, 



