266 Frederick Tilney, 



The nuclei are large and picnotic. The term picnotic is here used 

 in all instances in its histological sense and does not imply any de- 

 generative or other pathological changes in the nucleus. 



c) Vascularit}^ The pars distalis is conspicuous because of its 

 marked richness in a plexus of intercordai blood spaces. In this respect 

 it differs notably from the other regions of the gland. 



It will be argued that the part here described as the pars tuberalis 

 is included in the portion of the gland which the physiologists and 

 medical experimenters have defined as the pars intermedia. Herring [1] 

 has called attention to the fact that this part of the gland presents 

 two histologically distinct areas. One of these areas he describes as 

 the "toiigue-like process" of the pars intermedia, the other he terms 

 the ''epithelial investment" of the posterior lobe. The histological 

 details of these two areas are shown in his figures 8 and 9, pages 138 

 and 140 respectively. They are completely in accord with the findings 

 of the writer. ()n the other hand, there is nothing in Herring's papers 

 to show that he has recognized the actual form and relations of this 

 region or that he appreciates the developmental significance of the 

 structure which he describes as the pars intermedia. The studies of 

 the writer in the cat, dog, sheep, rabbit, rat and fowl, show conclus- 

 ively the marked morphological and histological differences between 

 the pars tuberalis and the pars infundibularis, thus making clear the 

 inaccuracy of grouping these two different parts under any such in- 

 adequate term as the "pars intermedia". Furthermore, the development 

 of the juxta-neural epithelial portion of the gland in the cat and 

 chick demonstrates that this part consists of two genetically distinct 

 elements, namely, the pars infundibularis, which arises as a part of 

 the original buccal evagination and is juxta-neural from its inception, 

 and the pars tuberalis which develops as a pair of relatively late 

 diverticula from the buccal evagination and secondarily assumes a 

 juxta-neural position. 



2. Adult Dog, Specimen no. H 80 (plate VIII, figs. 7 and 8). 



The same neural elements enter into the formation of the hypo- 

 physis as in the cat. The saccular eminence of the tuber cinereum 

 occupies the typical position on the floor of the third ventricle; it 



