TRANSACTIONS OF SECTION D. DEPT. ANATOMY AND PHTSIOLOGT. 719 



MONDAY, SEPTEMBER 5. 



1. On the Homologij of the Gonario-hypophysial Tract, or of the so-called 

 ^Pineal ' and ' Pituitary Glands.' By Professor R. Owen, M.D., C.B., 

 F.B.S. 



The author, referring to the latest contributions to the subjects of bis paper, 

 remarked that they bore upon the functions of the so-termed glands. Professor 

 Sapolini, in his work ' L'aire de la Selle Turcique ' (8vo., 1880), concludes that the 

 'pituitary gland secretes the fluid of the ventricles of the brain;' Professor Ed. 

 Vom Beneden, in reference to the supposed pituitary gland in Ascidians, regards it 

 as their renal excretory organ (' Archives de Biologie,' 8vo., 1881). 



In pursuance of his aim, ■which was homological, Professor Owen traced the 

 modifications of the pineal and pituitary bodies and connecting parts from man 

 down to the lowest fishes possessiag a brain ; and noted the progi-essive increased 

 relative size and retention of tubular structure of the tract including the so-called 

 ' pituitary gland,' ' infundibulum,' ' thii-d ventricle,' and ' pineal gland,' as the series 

 descended ; and he noted the further extension of the pineal part of the tract, beyond 

 the brain, to its perforation of the cranium, leaving the so-called ' foramen parietale ' 

 or cranial 'navel,' in some existing and in many extinct Reptilia. These phe- 

 nomena were then tested and compared with concomitant phases in the develop- 

 ment of the Vertebrate, especially the Mammalian, embiyo. It was shown, as 

 had been noted by previous embryologists, that, prior to the permanent anterior 

 outlet of the digestive sac, a production from such sac extended to the large 

 cerebral vesicle subsequently reduced to a ' third ventricle,' whence the hollow tract 

 was continued onward to the epithelial covering of the brain, by which it was 

 closed. The lower, pharyngeal, beginning of this tract also became closed and 

 modified, as the ' pituitary body' : the upper continuation became modified, and in 

 higher Vertebrates closed, as the 'pineal body ' ; but the intermediate portion of the 

 tract retained its primitive hollow condition as the ' third ventricle ' and 'infun- 

 dibulum.' The ' sella turcica ' in Mammals, like the ' foramen parietale ' in cold- 

 blooded Vertebrates, were modifications in the skeleton of parts of the primitive 

 ' conario-hypophysial tract.' This tract, under all its modifications, divided, or- 

 marked vertically, the division between the ' cerebrum ' and the ' optic lobes,' or 

 divided the ' fore-brain ' from the ' hind-brain.' 



The author next proceeded to point out the homologies of the parts of the 

 ' neural axis ' in Invertebrates with those in Vertebrates. 



The so-called ' supra-cesophageal ganglion or ganglions ' in the former were 

 homologous with the ' cerebriun or cerebral hemispheres ' in 'the latter. The so- 

 caUed ' suboesophageal masses ' in Invertebrates answered to the mes- and ep- en- 

 ceplialic masses in Vertebrates. The neural chords and ganglions continued therefi-om 

 in Invertebrates answered to or were homologous with the myelon or spinal chord 

 of Vertebrates, in which the ganglionic structiu'e was more or less concealed, save in 

 some fishes, by superadded neural substances. 



Now, the ' supra-oesophageal mass,' or ' fore-brain,' in Invertebrates was divided 

 from the ' sub-oesophageal masses,' or ' hind-brain,' by the production of a tubular 

 portion of the fore part of the primarily closed alimentary cavity; which, extend- 

 ing between those parts of the neural axis, opened upon the surface of the head so 

 attained, and there established the permanent ' mouth ' ; the tubular extension similarly 

 retaining its functional or oesophageal relations with the alimentary cavity. The 

 neural chords connecting the so separated fore-brain from tlie hind-brain, traversed 

 the sides of this gullet ; as the chords, or crura, proceeding to expand into the fore- 

 brain of Vertebrates, traverse the sides or walls of that persistent part of the conario- 

 liypophysial tract, known, in Anthropotomy, as the 'third ventricle.' The large 

 relative size of the embryonal brain-vesicle, in this relation, is significative of the 

 homology of the parts extending therefrom. 



Passing, next, to the consideration of the characters which had been held to 

 determine the ' back ' and ' beUy ' of an animal, the author cited ' coloiu-,' the rela- 



