Sorensen, Study of Epiphysis and Roof of Diencephalon. 1 3 



pinealis. The former gave no explanation of the projection 

 and the latter found no connection between the projection and 

 the pineal gland development. 



Meynert (57) considered the structure of the pineal gland 

 nervous, and thought it was the ganglion from which the teg- 

 mentum arose. 



Henle ( 32-71) took the pineal for a lymph gland which func- 

 tioned as such in the embryo, but later, as the stream of lymph 

 entered other courses, a degeneration took place. Further, 

 Henle found that the pineal in man consists of follicles (.06-. 03. 

 mm.) which are more or less separated from one another by 

 connective-tissue ; later the substance of the follicles is formed 

 of cells having the appearance of lymph bodies, still, for the 

 most part, somewhat larger (.015 mm.), of cubical form and 

 with globular nuclei. The union with the nervous system is 

 only external ; no fibres leave the commissure of the stalk to 

 enter the gland and the few nerve fibres present belong only to 

 the blood vessels. 



Bizzozero (6), contemporaneously with Henle, studied 

 the structure of the pineal gland. He describes a reticulum 

 in whose meshwork lie large and small cells provided with 

 projections ; in the new born the projections are wanting. 

 In addition to the foregoing casual references, Mihalcovics 

 gives an historical resume at the end of his paper, in which 

 he divides the investigators into three groups. First, 

 those representing in part the oldest views, who considered 

 only the exterior, as the size, form and consistency ; sec- 

 ond, those who recognised that the gland arises from an evagi- 

 nation of the roof of the diencephalon, but did not understand 

 the method; and third, those who explained the entire process 

 quite fully. 



Group I. Here belong J. and C. Wenzel ( brothers ), 

 Tiedmann, Serres, Rathke, and Reichert. 



J. and C. Wenzel (93-12. pp. 3 13-3 16) first saw the 

 gland in embryos of 5 months. It was about the size of the 

 head of a small pin, spherical and pale. The brain sand did 

 not appear until the 7th year. 



