Histological Appearances of the Maiinnalian Pituitary Body 



141 



numerous at the junction of the epithelium with the nervous portion (cf. 

 fig. 9). In the dog, capillaries are rather more numerous. In the monkey 

 they are absent. A very striking difference is thus afforded between the 

 highly vascular epithelium of the anterior lobe and the non-vascular 

 epithelium which covers the posterior lobe. This peculiarity indicates a 

 difference between the two parts, if not of function, at any rate of the mode 

 of absorption of the products of the epithelial cells. Another significant 

 feature relates to the position of the colloid material. This occurs for the 

 most part in extra-vascular situations, and never far distant from the 

 nervous portion of the pituitary. If it is a product of secretion utilised by 

 the animal, it must pass inwards to the nervous tissue and be carried away 

 by the numerous blood-vessels situated immediately under the epithelium, 

 or pass into lymph spaces in the nervous portion. This point will be dis- 

 cussed later in connection with the structure of the nervous portion. In 

 the other place, where colloid material is common in the cat, viz. in the 

 tongue-like process (fig. 8), the epithelium containing it is surrounded by 

 connective tissue, blood-vessels and lymphatics, and even here a close rela- 

 tion exists between the epithelial cells and adjacent brain substance. The 

 structure of the intermediate part of the pituitary body shows such marked 

 differences from the structure of the anterior lobe that it is quite probable 

 it has a different function. 



Structure of the Nervous Part of the Pituitary. 



On no part of the pituitaiy body have there been so many and different 

 opinions expressed with regard to structure as on the portion derived from 

 the brain. Virchow (46) regarded it as a "filum terminale anterius," 

 consisting of ependyma cells, networks cf white fibres, and finely 

 granular masses in which cells appear. He could find no nerve cells in it. 

 Peremeschko (30) described a feltwork of connective tissue fibres and 

 spindle-shaped cells, with a few ganglion cells among them. The latter, 

 he says, lie mostly two or three together surrounded by "connective tissue, 

 and differ from ordinary ganglion cells in that their protoplasm is scantier 

 and their nuclei flattened. W. Miiller (27) and Mihalkovics (25), who 

 studied the development of the pituitary, agreed that with the ingrowth of 

 blood-vessels into the nervous portion, a proliferation of connective tissue 

 cells accompanying them destroys the original brain tissue, converting the 

 infundibulum into a connective tissue appendage of the brain. W. Miiller 

 (27) compared the arrangement of the connective tissue cells to the appear- 

 ances shown by a spindle-celled sarcoma, a simile which has been frequently 

 employed since by authors of text-books of anatomy. Loth ringer (22) 

 described the bulk of the organ as made up of bundles of fibres, with nuclei 

 resembling those of plain muscle fibres, crossing one another at sharp angles, 

 and holding in the meshwork thus formed round, angular, or polygonal 

 cells. He believed it to be chiefly neuroglia tissue, and poor in nerve cells. 



