SORENSEN, Neurological Laboratory Notes. 49 



line with the terminal points. Between the post-parietal bone 

 and just above the nerve (to be described later) is a distinct 

 blood sinus, which was traced some distance toward the epiphy- 

 sis. The parietal organ is spheroidal in form and consists of 

 three parts, a lense and an inner and outer wall. The walls are 

 deeply pigmented and their histology has not yet been studied. 



The Epiphysis. The combination of structures arising from 

 the roof of the diencephalon, Mr. Ritter, in keeping with the 

 former nomenclature, designated as the Epiphysis. He the gave 

 the following parts: A proximal part with an anterior, much 

 folded, epithelial wall, and a posterior, not folded and thiner 

 epithelial wall ; an epiphysial vesicle ; a blood sinus; and a string 

 of connective tissue. From a study and comparison of his 

 drawings it is quite evident that what he has termed the ' proxi- 

 imal part with an anterior, much folded, epithelial wall ' is the 

 plexus formed anteriorly to the supra-commissure and found in 

 many groups ("Polster"of Burckhardt.) It is evident, moreover, 

 that no connection appeared in his sections between the '' epi- 

 physial vesicle" and the roof of the diencephalon. In the sec- 

 tions which I have studied, the following structures appear : 

 Epiphysis (epiphysial vesicle) ; epiphysial stalk ; nerve ; blood 

 sinuses; and plexus. 



The Epiphysis is prominent and cannot be mistaken. It 

 is composed of columnar epithelium very different from that of 

 the plexus and profusely pigmented and consists of a large num- 

 ber of diverticles from the same visicle. 



The epiphysial stalk connects it directly with the roof of 

 the diencephalon just back of the supra-commissure. There 

 can be no question that the so-called vesicle, with its stalk, con- 

 stitutes the true epiphysis which is in this case flexed cephalad at 

 the tip. Moreover the entire structure exhibits the same rela- 

 tions which are encountered in all other Sauropsida. 



The epiphysial Jierve wdiS traced through different sections 

 from its origin in the supra-commissure to its terminus just below 

 the parietal organ. No fibers, however, were found to enter the 

 organ. 



