Histological Appearances of the Mammalian Pituitary Body 143 



the opinion that, although nerve fibres may be present, the bulk of the 

 posterior lobe consists of neuroglia cells and fibres, and ependyma cells. 

 Kolliker (19) takes up the same position, and holds that the apparent 

 nerve cells are really neuroglia and ependyma ; many of the fibres of the 

 latter run for a considerable distance in a longitudinal direction, and form 

 thick bundles. Kolliker agrees with Retzius, that, in man and the 

 higher mammals, there are no true nerve elements in the infundibular lobe, 

 and that the occurrence of glandular structures in it betokens the formation 

 of an infundibular gland in the sense of Kupffer. 



The posterior lobe of the pituitary body, when fixed in formalin, cor- 

 rosive sublimate, or other fixing agent in common use, and stained in thin 

 sections by hsematoxylin and eosin, presents in its interior a structure which 

 has a general resemblance to connective tissue. There are numerous 

 flattened, spindle-shaped, and branching cells, and a matrix large in amount, 

 finely granular, and holding numerous ill-defined fibres resembling white 

 fibrous tissue. Blood-vessels are fairly numerous, especially small arteries 

 and capillaries, and the tissue of the nervous lobe frequently appears to be 

 arranged in whorls around them, a layer of condensed matrix lying next 

 the vessels, and outside that a lighter zone anastomosing with similar 

 layers around adjacent vessels. This disposition of the matrix is very well 

 brought out by the iron-alum-heematoxylin method of staining. A some- 

 what similar arrangement is seen in the neck of the infundibulum, where 

 there are two very distinct layers surrounding the central cavity, an inner 

 layer in which run longitudinally placed fibres, and an outer layer, which 

 is finely granular and apparently traversed by much finer fibres, having for 

 the most part a vertical direction. 



The cells in the posterior lobe do not resemble true nerve cells, and 

 when the sections are stained by Nissl's method nothing of the nature of 

 Nissl bodies is found in them. In sections prepared by Cox's modification 

 of Golgi's method, the nervous substance is seen to be composed of neu- 

 roglia cells and fibres (fig. 10). 



The neuroglia cells are numerous, and their branches interlace, forming a 

 dense network of fibres througliout the body of the infundibulum. Many 

 of the branches end in relation to the blood-vessels, which they frequently 

 bend round ; others run to the periphery of the lobe, but do not penetrate 

 into the epithelial investment. In addition to the neuroglia cells and fibres, 

 there are cells lining the central cavity, continuous through the neck of the 

 infundibulum with the cells that line the cavity of the third ventricle. 

 They are undoubtedly ependyma cells, and are extremely well developed in 

 the pituitary. The fibres from the cells take various directions, according 

 to the position of the cell bodies, but most of them assume a longitudinal 

 direction, and pass into the neck of the infundibulum. In this .situation 

 they at first run in the internal layer, then turn into the outer layer, and. 

 breaking up into extremely fine fibrils, take a course at right angles to theii- 

 previous direction, and end at the margin of the neck in proximity to the 



VOL. I. — APRIL 1908. 10 



