Histological Appearances of the Mammalian Pituitary Body 153 



whether the colloid substance of the pituitary is identical in composition, 

 or in its physiological action, with the colloid of the thyroid gland. The 

 physiological action is apparently quite different, but this may be due to 

 the presence in the lobe of other substances. Any secretion formed in the 

 pars intermedia of the pituitary must pass into the adjacent substance of 

 nervous origin either by blood-vessels or lymphatics. There is a possibU- 

 exception to this rule in the tongue-like process of the cat's pituitary, but 

 even here blood-vessels from it pass into the adjacent anterior lamina 

 connecting the neck of the infundibulum with the tuber cinereum, and tla- 

 tubules are surrounded by connective tissue containing l^n^nphatics, the 

 course of which is unknown. They may possibly accompany the blood- 

 vessels. The epithelial cells do not resemble in staining properties the 

 cells of the medulla of the suprarenal capsule ; they have no affinity for 

 chromic acid. Nor do they resemble them in their relations to blood- 

 vessels, the absence of which is so characteristic of most of the pars 

 intermedia. 



A question of importance arose in the earl}" investigations of the 

 structure of the pituitary. Peremeschko (30) described the cleft of the 

 epithelial part as being continuous with the central cavity of the neck of 

 the infundibulum, and so with the third ventricle of the brain. If this 

 were the case it would furnish a proof of Kupffer's view (21) that the 

 epithelial portion represents a " palseostoma " or old mouth of an ancestral 

 form of vertebrate, and there would be in the mammalian embryo a 

 communication between the neural canal and buccal cavit}^ Subsequent 

 observers have denied the accuracy of Peremeschko's observations. In 

 the pituitaries of the pig and man, in which Peremeschko described the 

 continuation, there is obviouslj^^ no such thing, for the body of the infundi- 

 bulum is solid in both cases. Nor is there any indication of it in the 

 embryo of either pig or man, so far as I have been able to see. It is far 

 more likely to occur in the pituitary of the cat, in which the central cavitj* 

 of the infundibulum is well developed and prolonged far backwards. In 

 the adult cat the epithelium, as already stated, frequentl}' invades the 

 posterior end of the cavity, so that epithelial cells may even form part of 

 its lining. This peculiarity affords some support for Kupffer's view. In 

 the adult cat I have never been able to find a direct coinmunication 

 between the cleft and the cavity of the infundibulum, although many 

 specimens have been examined with this object. In one embryo kitten, 

 however, I have found such a connnunication. Cleft and cavit}' in this 

 specimen are undoubtedly in direct continuity at the postero-superior 

 angle of the posterior lobe. In other kittens, at a comparativeh' late stage 

 of embryonic life, a direct continuity' is occasionally seen between tubular 

 epithelium at the end of the cleft, and the ependyma cells lining the 

 central cavity of the infundibulum. In the kitten this coming together 

 of the two portions occurs some time after the epithelial duct between 

 buccal mucous membrane and epithelial portion of the pituitary has 



