HYPOPHYSIS CEREBRI OF CALIFORNIA GROUND-SQUIRREL 201 



curve outward along the periphery of the nervous lobe where 

 they can be traced for a short distance. Those fibers in relation 

 to the pars infundibularis come to lie in a thick layer adjacent to 

 the gland tissue, and separated from it only by the series of 

 vessels already mentioned. The pars neuralis is supplied by small 

 arterial branches which enter at its posterior end, where, in sec- 

 tions, there is always a break at the point of entrance. Through- 

 out the part, small vessels are very evenly distributed, but these 

 are not very numerous. Nothing was seen of nerve cells. Many 

 neuroglia and ependyma fibers course through the lobe. 



777. The colloid 



The subject of hypophyseal colloid is fully summarized by 

 Stendell ('14) and is treated in detail in several papers, but usually 

 only as applied to the pars infundibularis. Here, to be sure, it 

 is found in great abundance, but it is also very noticeable in the 

 pars distalis in several of the forms which I have observed. In 

 the ground-squirrel hypophysis the cysts are very numerous in 

 the pars distalis, but usually quite small as compared with those 

 of the pars infundibularis, being 6/x to 8/x in diameter in the former 

 and up to Sn to 15 ix and even larger in the latter. 



The cysts of the glandular portion (pars infundibularis and 

 pars distalis) can be conveniently divided into two groups accord- 

 ing to the character of the contents. In one type the material 

 is apparently made up of the remains of broken-down cells (fig. 

 10). The second type presents a wholly different picture 

 (fig. 9). The contents of these are hyaline. They never show 

 any particles which could in any way be associated with cell 

 remains. This type is not confined exclusively to any particular 

 area, but is, however, far more common in the pars infundibularis. 

 These colloidal masses appear to have a darker peripheral portion 

 probably due, however, to refractive differences alone. External 

 to this sharp border, the surrounding cells are usually arranged 

 radially. 



In spite of close study, I have never found cysts in the pars 

 infundibularis showing any communication with the cavity of 



