HYPOPHYSIS CEREBRI OF CALIFORNIA GROUND-SQUIRREL 191 



pars inf undibularis and the pars distalis are not entirely separated, 

 a transition zone is found to exist at the periphery of the lumen 

 where the one portion merges into the other. 



The hypophysis of the ground-squirrel (fig. 1) measures about 

 2 mm. in the anteroposterior dimension and 2.5 mm. trans- 

 versely. The dimensions vary somewhat in a series of measure- 

 ments, but the ratio of length to breadth is quite constant. The 

 organ lies in a shallow sella turcica, to which it is firmly bound by 



Cv-- ' ' w : >■& ::y ~ ->'•-. '* V <± i 

 •-■-■•- -. v ■■\\s-v-- .'</:•'.•"-•/■— '-->. 



Fig. 2 Section somewhat lateral to fig. 1 (semi-diagrammatic). B, brain; 

 SB, sphenoid bone; PN, pars neuralis; PI, pars inf undibularis; RL, residual 

 lumen; PG, pars distalis; D, dura. X 25. 



the meninges. Considerable care has to be used to avoid break- 

 ing or tearing the infundibulum during removal. The infun- 

 dibulum lies amost horizontally in the anteroposterior direction, 

 and is bordered on either side, as in all the higher forms, by the 

 corresponding optic tract. The glandular portion is a deep blood 

 red and the nervous portion a glistening white in the fresh con- 

 dition. The glandular portion partially envelops the pars 

 neuralis and extends further posteriorly at its lateral margins 

 than elsewhere, thus forming a concave hinder surface (figs. 1 and 



