GENETIC TYPE AND THE ENDOCRINES 449 



of the pars nervosa. The residual lumen of the embryonic 

 Rathke's pouch persists as a space separating the pars 

 tuberalis and pars distalis from the pars intermedia. The 

 pars intermedia closely envelops and fuses with the pars 

 nervosa and its epithelial cells invade the nervosa to varying 

 depths, forming follicles, cords and islands of cells. Various 

 regions of the intermedia itself also give rise to follicles 

 containing a colloid-like material closely resembling the small 

 follicles of the thyroid. Several of these are seen at the 

 distal end of the section in figure 1 (pi. 87). 



A portion of the anterior pituitary extends along the in- 

 fundibular stalk completely surrounding it and passing for- 

 ward ventrally toward the optic chiasm. Tilney ( '13) has very 

 appropriately termed this part the pars tuberalis. Evagina- 

 tions extend out from the residual lumen of Rathke's pouch 

 as epithelial diverticula, particularly in this region of the 

 pars tuberalis, as Atwell first pointed out ('18, '26). Alveoli, 

 follicles or acini are more numerous and constant in the pars 

 tuberalis than elsewhere. Also in this pars tuberalis region 

 the remains of the epithelial stalk which connected the em- 

 bryonic hypophysis with the buccal epithelium may persist 

 in some breeds, although it has entirely disappeared in the 

 dachshund and most other long muzzled types. However, this 

 stalk frequently persists as an embryonic arrest in the short 

 muzzled bulldog group and at times in the acromegalic giant 

 breeds. The hypophyseal foramen through the basisphenoid 

 may be patent, permitting direct connection between the 

 pbaryngeal lining and the glandular pituitary, as mentioned 

 in an earlier section and illustrated in plate 53 (p. 285). The 

 distal portion of the hypophyseal stalk and the diverticula 

 from the residual lumen in the pars tuberalis region are fre- 

 quently involved in extensive cystic formations within the 

 anterior pituitary of many dog breeds. 



The above details, quite typical of the dog pituitary, are 

 clearly illustrated by the dachshund gland. But, as intimated, 

 the glands from all dachshunds are not so nearly perfect as 



