An Analysis of the Juxta-Neuial Epithelial Portion etc. 263 



Description of the Pars Tuberalis. 



1. Adult Domestic Cat, Specimen no. H50a; fplate V, figs. 1 and 2). 



The neural elements entering into the hypophysis of the cat 

 comprise 1, the saccular eminence of the tuber cinereum; 2, the in- 

 fundibulum; and 3, the infundibular process. All of these structures 

 pertain to the floor of the third ventricle and acquire their particular 

 form and relafions during the relatively late stages of development. 

 The third ventricle follows the general plan of this chamber with its 

 principal plane vertical; in the hypophysis region, the chamber rapidly 

 expands laterali}^ on both sides and thus gives rise to a large ventral 

 recess whose chief plane is horizontal. This ventral recess of the 

 third ventricle has its surface expression in the eminentia saccularis 

 of the tuber cinereum. In its general appearances this protuberance 

 resembles one-half a clam shell. Its greatest convexity occurs at the 

 junction of the gradually sloping ventro-cephalic surface [9a] and the 

 more declivitous caudal surface [9h]. The ventro-cephalic surface 

 rises slowl}^ to the region immediately caudad of the chiasm, while 

 the caudal surface ascends abruptly to a small pi-emammillary area [6] 

 cephalad of the corpora mammillaria. Laterally the diverticulum 

 extends outward for a considerable distance on either side and each 

 lateral extremity becomes free from its connection with the overlying 

 portion of the eminentia lateralis. The part of the third ventricle 

 defined by this diverticulum is the recessus tuberis [17]. 



On approaching the sagittal plane the ventro-cephalic [9a] and 

 the caudal surfaces [9b] of the saccular eminence become ventro- 

 caudally drawn out into a funnel shaped process, the infundibulum [10]. 

 At the caudal extremity of the stem of the infundibulum there appears 

 a large mass of neural tissue, the processus infundibuli [11]. The 

 cavity contained in the infundibulum is the recessus infundibuli [6'], 

 that in the processus is the recessus processi infundibuli [16]. A recon- 

 struction representing a cast of the lower part of the third ventricle 

 with these appended recesses is shown in plate VI, fig. 3. 



The epithelial portion of the hypophysis consists of three elements; 

 namely, the pars tuberalis, the pars infundibularis and the pars distalis 

 (plate V, fig. 1). The pars tuberalis is moulded to the base of the 



