THE HISTOGENESIS OF DENSE LYMPHATIC TISSUE 163 



liolic eosin, washed in water, then carried into the methylene- 

 bkie solution, after which they were differentiated, dehydrated, 

 cleared, and mounted as for the Hastings-Nochts stain. 



Another stain, proving of no little value in bringing out cer- 

 tain specific features, was a mixture composed of equal parts of 

 1 per cent aqueous solutions of methyl green and pyronin (after 

 Pappenheim). After staining in this solution for ten minutes, 

 the sections were washed in water, and carried immediately 

 into a 1 per cent solution of resorcin in absolute alcohol for differ- 

 entiation and dehydration, cleared in xylene, and mounted in 

 xylene damar. 



For the purpose of sharply differentiating the reticular tissue 

 from the free cells of the lymphatic tissue, Mallory 's connective- 

 tissue stain was used, after first mordanting the sections for a few 

 minutes in picro-acetoformalin. 



Other special methods were used at various times to bring out 

 or make clear certain specfic features of these structures. These 

 methods will be discussed as the features made clear by their 

 use are spoken of. 



In the study of the histogenesis of the elements of the connec- 

 tive tissue (tunica propria and submucosa) in the region of the 

 formation of the intestinal tonsils, it is noted that, coincident 

 with the formation of lymphatic tissue, other cellular elements 

 of the blood may be developing also. 



It has long been a matter of common knowledge that, in the 

 connective tissue of the wall of the digestive tract, varying 

 numbers of cells are found, in the cytoplasm of which are gran- 

 ules of either an eosinophilic or basophilic character. As has 

 been stated, the granules of basophilic character are readily 

 soluble in water and consequently were not found in any of the 

 preparations used, being dissolved out in the course of the 

 preparation. But the cells with eosinophilic granules are found 

 present, often in extraordinary abundance, in the connective 

 tissue in the neighborhood of the lymphatic nodules, more par- 

 ticularly in the tunica propria (figs. 9, 10, 11, 14, 16). 



Also, at certain stages in the development of the tonsillar 

 lymphatic tissue, there may be found, in apparent association 



