Histological Appearances of the Mammalian Pituitary Body 129 



cleft. At other times they end abruptly, and there is nothing but a thin 

 layer of connective tissue with occasional epithelial cells in it extending 

 backwards from the posterior margin of the anterior lobe to the reflection 

 on to the posterior aspect of the infundibulum. The thinning and partial 

 disappearance of epithelium in this situation in the adult cat may possibly 

 allow a communication between the cleft and the subdural space, but there 

 is no direct opening to be seen, and where the epithelium persists, as it 

 often does, serial sections show that the cleft is completely closed by it. 

 The readiness with which rupture may take place here is easily appreciated 



Flo. 4.— Mesial sagittal section through the j>ituitary bo<ly of 



an adult dog. (Senii-diagraminatic.) 



rt, optic cliiasnia; b, tongiie-like process of pars iiitermeiiia ; c, third ventricle; d, anterior lobe proper ; 



d\ part of anterior lobe appearing above; e, epithelial cleft; <t, nervous subsUnce of posterior lobe : 



i, epithelial investment of posterior lobe. , .^. , ^, .^, ,. 



The dark shading indicates the anterior lo))e proper ; the lighter shading sIk.ws the position of the epithelium 



of the pars intermedia. 



from the appearance in tig. 8, which is a photograph of an actual specimen 

 of the cat's pituitary. 



The pituitary body of the dog (tig. 4) presents furtluT ditierences in the 

 structure and arrangement of its parts. The body of the posterior lobe is 

 solid, but a cavity occurs in its neck which opens by a comparatively wide 

 mouth into the tliird ventricle of the brain. 



The attachments of the pituitary body to the base of the brain are very 

 similar in the cat and dog. A thin lamina of brain sub-stance runs forwards 

 from the neck of the infundibulum for some distance to merge with the 

 tuber cinereum. This lamina is closely invested below by the tongue- 

 shaped process of epithelium which runs forward from the anterior lobe. 



