THE DUCTLESS GLANDS. 197 



nations are distributed to the walls of the vessels and penetrate 

 between the epithelial cells of the parenchyma. 



As in the case of the thyroid gland, the relations of the epithelial 

 cells of the adrenal bodies to the lymphatics appear of special 

 interest. The lymphatic vessels are abundant and large, and accom- 

 pany the bloodvessels lying in the areolar tissue of the septa. 

 Here they come into close relations with the columns of epithelial 

 cells, and, at least in the cortex, send minute terminal branches 

 into those columns, where they end among the epithelial cells (Fig. 

 172). This arrangement of the lymphatics appears to point to the 

 elaboration of an internal secretion as the function of the adrenal 

 bodies. Small masses of lymphadenoid tissue are occasionally 

 observed in the cortical portion of the adrenal body. 



4. The Pituitary Body. — The pituitary body (hypophysis cerebri) 

 is divisible into two portions, which differ both in their structure 

 and in their embryonic origins. The posterior, or nervous, lobe is 

 derived from a prolongation of the third cerebral ventricle. The 

 anterior, or glandular, lobe develops from a tubular prolongation, 

 lined with epithelial cells, from the buccal cavity of the embryo. 

 This partially or completely invests the nervous portion of the 

 body, but its chief bulk is situated in front. The connection with 

 the buccal cavity is obliterated, and, in the further development of 

 the detached portion, a number of anastomosing columns of epi- 

 thelial cells are formed, which are separated from each other by 

 septa of vascular areolar tissue. These septa become continuous 

 at the periphery Avith a thin fibrous capsule furnished by the pia 

 mater. 



The cells of the epithelial strands in the glandular lobe appear 

 to be of two sorts, which, like those in the thyroid gland, probably 

 represent different stages of functional activity. The darker sort 

 of cell yields microchemical reactions resembling those of colloid ; 

 and little masses of colloid, presumably derived from those cells, 

 are of not infrequent occurrence within or at the margins of the 

 epithelial columns (Figs. 173 and 174). 



The glandular lobe is richly supplied with capillary bloodvessels 

 in intimate relations with the epithelium, from which they often 

 appear to be separated by only a thin basement-membrane, and the 

 existence of this is doubtful in some situations (Fig. 175). 



The above description shows that the structure of the hypophysis 

 is similar to that of the other ductless glands already considered. 



