Histological Appearances of the Mammalian Pituitary Body 127 



The gland lies on the body of the sphenoid bone, and is separated from it 

 by the dura mater, which is thickened in front and behind, and contains 

 blood-vessels, and what appears to be a lymph space. This space, which 

 was described by B. Haller, is not a marked feature in the kitten, but is 

 more pronounced in the foetus of the ox, where, at an earlier stage in 

 development, it penetrates for some distance into the body of the sphenoid 

 bone. Ossification of the bone at this point is delayed by the gradual 

 disappearance of the epithelial stalk which connects the anterior lobe of 

 the pituitary with the buccal epithelium. No trace of this connection is 



Fio. 2. — Mesial sagittal section through the pituitary body ot" 

 an adult cat. (Semi-diagrammatic.) 



a, optic chiasma ; b, tongue-like process of pars intermedia ; 



, epithelial cleft ; /, cavity of posterior lobe ; /', cavity of neck of posterior lobe : 



third ventricle ; d, anterior lobe proper ; 

 fj, nervous substance 

 of posterior lobe ;' i,' epithelial investment of posterior lobe. 

 The dark shaiiing indicates the distribution of the characteristic cells of the anterior lobe ; the lighter shading 

 shows the position of epithelium belonging to the pars intermedia. 



found in the new-born kitten, and there is no evidence of any opening of 

 the glandular tubules or cleft of the pituitary into the lymph space either 

 in the foetal ox or kitten. 



The pituitary body of the adult cat is ver}^ similar in structure to that 

 of the kitten, but presents several important modifications. In mesial 

 sagittal section the posterior lobe appears larger than the anterior; the 

 latter is, however, the larger, and extends further laterally, embracing the 

 posterior lobe. The central cavity of the posterior lobe persists, and a 

 tapering process of it runs upwards and backwards towards the place of 

 entry of the blood-vessels into the infundibulum (fig. 2). This process is 



VOL. I. — APRIL 1908. 9 



