THE PINEAL BODY 15 



system manifests this same disposition, for here the brain curves 

 itself backward in such a way as to constitute a ring above the 

 region destined to become the mouth, thus producing a deep 

 fossa directed toward the brain. Owen regards this as part of a 

 canal which traverses the brain, now disposed as the oesophageal 

 ring of articulates. Early, however, the process is arrested and 

 the tube-like invagination comes to form the pituitary gland. 

 The original tube from the mouth region is completed by an 

 invagination from the dorsal region of the head which is con- 

 nected with the skin. This element becomes atrophic and its 

 remains constitute the pineal gland. Baraldi ('84) 13 modified 

 the theory of Owen by stating that the hypophysis was a deriva- 

 tive of the wall of the mouth of the gastrula or, in other words, 

 the last vestige of the extreme anterior portion of the alimentary 

 canal of worms. Robin's 334 idea seemed to offer some confirma- 

 tion to this opinion in the fact that he found in the epiphysis, 

 upon microscopic examination, a follicular, gray substance con- 

 taining a granular liquid very similar to that in the intestines. 

 Schwalbe ('81) 348 found medullated nerve fibers which ac- 

 company the blood vessels and come into relation with bipolar 

 and multipolar cells in the pineal body. He believes there 

 existed some similarity between the pineal body and lymph 

 corpuscles, but regards the cells of the former to be modified 

 epithelial elements. Ganser ('82) 142 thought the pineal body to 

 be an unpaired process of the ganglion habenulae. Flechsig 

 ('83) 124 maintained that the epiphysis sends fibers to the fascicu- 

 lus retroflexus. Sappey ('87) 344 considered the pineal body 

 analogous to the substance of the cerebral cortex. Mingazzini 

 ('89) 276 regarded the elements of the pineal body as similar to 

 those of the lymphatic corpuscles. Moller ('90), 278 investigat- 

 ing the epiphysis in the chimpanzee, distinguishes an unpaired 

 peduncle which constitutes the largest part of the pineal body. 

 The organ itself is 3 mm. x 2 mm. long. The peduncle is 4 mm. 

 long and consists of nervous tissue. The pineal recess is ex- 

 tensive. Moller regards the structure as a rudimentary organ 

 in a retrograde state. Charpy ('94) 62 considers the epiphysis as 

 a degenerating organ made up exclusively of epithelial elements 



