An Analysis of the Jiixta-Neural EpitheHal Portion etc. 267 



presents a ventro-cephalic \9a] and a caudal surface \9b] whose general 

 relations are almost identical with those in the cat. It also has the 

 two lateral, free extremities. It is, however, a less extensive pro- 

 tuberance and therefore forms a relatively small portion of the floor 

 of the third ventricle. 



The Junction of the ventro-cephalic and caudal surfaces is drawn 

 out in the usual manner to form the infundibulum, although the tran- 

 sition from tuber cinereum to infundibulum is less well marked than 

 in the cat, due to the fact that the protrusion from the tuber is not 

 confined to the sagittal planes but involves the greater part of the 

 junction between the ventro-cephalic and caudal surfaces. The infundi- 

 bulum terminates caudally in a solid infundibular process. Because 

 of the relatively small size of the tuber cinereum, the premamraillary 

 area [61 is correspondingly increased. As in the cat, the recessus 

 tuberis is present, having its chief plane at right angles to that of 

 the third ventricle. The recessus infundibuli is also present but not 

 as conspicuously funnel-shaped as in the cat. The recessus processi 

 infundibuli is wanting. 



The epithelial portion of the hypophysis presents three distinct 

 portions, i. e. the pars tuberalis, pars infundibularis and pars distalis. 

 The pars tuberalis is adherent to the saccular eminence upon its 

 ventro-cephalic and caudal surfaces while along the more medial 

 portion of the junction between these two surfaces it presents a hiatus 

 through w^hich the infundibulum passes ventral to join the infundi- 

 bular process. The pars infundibularis completely invests, and is 

 adherent to, the infundibulum and infundibular process. The pars 

 distalis [14] is separated from the pars tuberalis and pars infund- 

 ibularis [13] by spacious residual lumen [15] and represents the largest 

 part of the pituitary gland. From the relations of the neural and 

 epithelial portions of the hj-pophysis in the dog it is clearly objec- 

 tionable to describe a posterior neural and an anterior glandular lobe, 

 since the pars neuralis is dorsal to the epithelial portion. 



The three epithelial divisions may be distinguished by their 

 histological characteristics: 



1. Histological characters of the pars tuberalis (plate XVI, fig. 29). 



