NEUROSECRETION IO4I 



FIG. I. A. Schematic diagram of the preoptic-hypophyseal tract in Anura. [From Hild (164).] 

 B. Schematic diagram of the neurosecretory elements of the hypothalamic-pituitary system in mam- 

 mals (dog and cat), including the supraoptic {i.o.)-paraventricular ip.i'.) tract to the intermediate 

 and posterior lobe and the tuberoinfundibular tract {l.l.i.). Of particular interest is the relationship 

 of these fibers to the roots of the portal vessels in the median eminence. Chromhematoxylin-stained 

 fibers from the anterior hypothalamus are situated in the more ventral part of the stalk (central zone, 

 ^^) and come into relationship with the 'special vessels' (232). Axons of the tuberoinfundibular 

 tract, not stained with chromhematoxylin, are collected near the peripheral zone (P^) and pass 

 nearer the base of the special vessels. The enlargement {insert) indicates these relationships: p.t., 

 nucleus principalis tuberis; inf., nucleus periventricularis infundibularis; /)./;., area periventricularis 

 posterior; ch., optic chiasma; t.s.li., supraopticohypophyseal tract; m., mammallary body; p., portal 

 vessels; a.h.s., branches of the superior hypophyseal artery. [Modified from Engelhardt (100) and 

 Bargmann (29).] 



