156 FREDERICK TILNEY AND LUTHER F. WARREN 



protuberance in front of the epiphysis in the new-born Bos 

 taurus. As a rule, the proximal portion is solid in the greater 

 part of its extent and attached by a more or less constricted 

 portion to the roof of the interbrain. This part of the epiphysis, 

 sometimes referred to as the stalk, is not to be confused with the 

 stalk of the lower vertebrates which, together with the end- 

 vesicle, fails to develop in mammals. The mammalian stalk is 

 more properly designated the pineal peduncle. The solid por- 

 tion of the epiphysis is regarded by many as a glandular struc- 

 ture, and hence the term pineal gland. In mammals the follow- 

 ing parts may be defined: The epiphysis or pineal body which 

 consists of 1) the pineal gland and 2) the pineal peduncle. In 

 the latter there is a recess of greater or less extent, the pineal 

 recess. The peduncle consists in a large part of nerve fibers, 

 while the pineal gland comprises several different constituents. 

 In man the peduncle becomes so specialized in the nerve fibers 

 which enter it as to constitute, according to some authorities, 

 distinct peduncular bundles or epiphyseal peduncles. 



The form of the pineal body in mammals varies considerably. 

 It is for the most part cone-shaped ; it may be long or relatively 

 short. In marsupials it is round or pyriform. In rodents it is, 

 according to Flesch, 121 more or less cylindrical, or, as Cutore 76 

 states, cylindricoconical. In the pig, d'Erchia 109 describes it as 

 spindle-shaped. In carnivores and primates the organ is gen- 

 erally conical or oval. According to Schwalbe ('81), 348 it is a 

 dorsoventrally flattened globule. In the primates the peduncle 

 is paired, with the exception of Troglodytes niger, in which, 

 according to M oiler ('90), 279 the epiphysis is kidney-shaped and 

 connected with the brain by means of a single unpaired stalk 

 4 mm. in length. The epiphysis in most mammals is dorsiflexed 

 so that its free extremity is directed toward the cerebellum. It 

 thus presents a ventral surface in relation with the midbrain, 

 a dorsal surface usually in relation with the corpus callosum 

 (although there are certain exceptions to this statement), a 

 base related to the roof of the interbrain, and an apex. The 

 dorsal surface is in contact with a reduplication of the dorsal 

 sac known as the lamina superior pediculorum and also with 



