HISTOLOGY OF THE HYPOPHYSIS CEREBRI 707 



(Figs. 1 and 2) that the infundibular process, as it enters the sella 

 turcica, is closely surrounded by the diaphragma sellse, which is formed 

 by a fold of the dura mater. The dura mater continues ventrally 

 and lines the entire sella turcica, being closely adherent to the bone. 

 The relations of the arachnoid are variable. It is usually reflected from 

 the infundibulum at the diaphragma sellse, but it occasionally extends 

 further ventrally and partially encloses the hypophysis as it lies in the 

 sella. When this is the case, there is greater danger of meningitis 

 through opening the subarachnoid space during operations (Lewis). 



Lobes. The two lobes can easily be distinguished in the gross. The 

 anterior lobe is larger and firmer in consistency and partially encloses 



Fig. 3. Median sagittal section of injected hypophysis showing high vascularity 

 of the anterior lobe as compared with the posterior lobe. (From Schafer, after Herring.) 



the posterior lobe in a hilus-like depression in its caudal surface. On 

 section it becomes apparent that the two lobes are also quite different in 

 color; for the anterior lobe has usually a reddish tint, owing to its rela- 

 tively high vascularity (Fig. 3), while the posterior lobe is often 

 greenish yellow, depending upon the amount of contained pigment. On 

 close examination of the anterior lobe, it is possible to define the limits 

 of the pars intermedia, which is a thin epithelial layer between the an- 

 terior lobe proper, in front, and the posterior lobe, behind. The pars 

 tuberalis, which is so distinct in lower forms, is only represented in man 

 by an inconspicuous prolongation of the tissue of the anterior lobe along 

 the infundibulum in the direction of the tuber cinereum, hence the term, 

 "tuberalis." 



Blood Supply. The blood supply of the hypophysis springs -from two 

 sources, from the internal carotids as they are passing through the caver- 



