180 JOHN STEPHENS LATTA 



sive divisions of one which had invaded the epithehum. The 

 lymphocytes in the intestinal tonsils, as opposed to those in 

 the tonsils of the mouth and pharjmx, rarely, if ever, wander 

 through the epithehum into the intestinal lumen. 



An interesting feature of the epithelium covering the lymphatic 

 villi is the lack of goblet cells, which are so plentifully found 

 elsewhere in the intestinal epithelium (Muthmann, Hartmann). 

 In a study of the early developmental stages, it is found that 

 goblet cells are numerous in the epithelial covering of all the 

 villi. Glands (crypts of Lieberkiihn) are not present as such 

 until later (showing that goblet cells are not, necessarily at least, 

 derived from the intestinal glands), but the epithelium between 

 the bases of the villi is of a different character. In these regions 

 no goblet cells were found. The places of nodular formation are 

 in the tunica propria directly below places where there is an 

 epithelium of this nature, and from these places the lymphatic 

 villi arise usually, the epithelium being gradually forced upward 

 between the ordinary villi as the lymphatic tissue increases in 

 amount, the original character of the epithelium between the 

 bases of the villi being maintained (i.e., without goblet cells). In 

 a few instances, goblet cells were found in the epithelium of some 

 of the lymphatic villi before its infiltration with lymphocytes 

 occurred. The lack of goblet cells in the epithelium covering the 

 lymphatic tissue is doubtless due to change in function of the 

 epithelium, brought about by its relation to the lymphocytes 



(fig. 12). 



The fundamental reasons for the development of lymphatic 

 tissue, especially of the tonsillar lymphatic tissue, and the com- 

 plete function performed by it are perplexing problems. 



The only definite function which has been ascribed to lym- 

 phatic nodes is the production of lymphocytes. This surely is a 

 function, but whether it is their only one is doubtful. Then the 

 question arises as to whether tonsillar lymphatic tissue has other 

 function than does the lymphatic tissue in other places. Some 

 authors consider that, in the light of our present knowledge of 

 tonsillar tissue, the only function that can be accurately ascribed 

 to it is that similar to the function of lymphatic nodes; i.e., 



