464 J. A. BADERTSCHER 



by far the most numerous, large ones are still plentiful in all 

 parts of the cortex. Even with a magnification of 1300 diameters 

 eleven were counted in a single microscopic field. All grada- 

 tions between the large and small ones are present. Mitoses 

 of all the different types occur. 



The medulla is still quite sharply defined from the cortex. 

 It contains less lymphocytes than the cortex. In some places 

 where the medulla of the lobules joins with that of the central 

 stem it comes in contact with the deep portion of the interlobular 

 septa. It contains all the different types of lymphocytes that 

 are present in the cortex and mitoses among them can be demon- 

 strated without much difficulty. Hassall's corpuscles are more 

 numerous than in the 180 mm. stage and an occasional one can 

 still be found in the process of formation. 



In the medulla the strands of the reticulum are often wavy 

 and in general are much coarser than those of the cortex. Also 

 •the epithelial nuclei are on the whole larger and clearer, and 

 surrounded by a more generous amount of cytoplasm than those 

 in the cortex. Mitoses of epithelial nuclei in both the cortex 

 and medulla can only very seldom be found. In sections treated 

 with Mallory's connective tissue stain fibrillae can be seen to 

 come off from the interlobular septa and the capsule and extend 

 a distance of from one to four cells deep into the cortex. In 

 both the cortex and medulla the same condition prevails between 

 the adventitia of the larger blood vessels (which are very few) 

 and the reticulum. I was unable to determine whether the 

 connective tissue fibers fuse with the reticulum. This intimate 

 relation of the connective tissue of the septa and of the large 

 blood vessels to the reticulum was observed by Mietens ('08) 

 but denied by Maximow ('09 b). No connective tissue fibers 

 aside from those mentioned above could be demonstrated in 

 either the cortex or medulla. Bell, however, by using Jack- 

 son's modification of Mallory's stain states that he was able to 

 demonstrate them thinly scattered through both the cortex 

 and medulla in all late developmental stages. 



The interlobular connective tissue septa are greatly reduced 

 in thickness, being widest in those places which lodge the larger 



