INTERNAL SECRETION 499 



as more than 51 per cent, of animals survived the operation for a prolonged 

 period and of these 68 per cent, showed no specific symptoms of any kind. 

 From the contradictory observations it is evident that the subject needs 

 further investigation. 



THE PITUITARY 



The pituitary is a small body lodged in the sella turcica of the sphenoid 

 bone. It measures 14 mm. from side to side, 8 mm. from before backward, 

 and 6 mm. from above down, and consists of an anterior lobe somewhat 

 pink in color, and a posterior lobe yellowish-gray in color. The anterior 

 lobe is much the larger and partly embraces the posterior lobe (Fig. 250). 

 The anterior lobe is developed from an invagination of the ectoderm of the 

 buccal cavity and consists of gland tissue surrounded by a thin envelope of 

 connective tissue. It becomes separated from the mouth by the fusion of the 

 sphenoid cartilages. The posterior lobe is an outgrowth from the mid-brain 

 and is connected with the infundibulum of the third ventricle by a short 

 stalk. In the early stages of its development it presents a central cavity 

 which is, however, soon obliterated by the growth of special tissues. It 

 persists in the cat. It has been suggested that the term 

 hypophysis cerebri be reserved for the anterior lobe and 

 the term infundibular body for the posterior lobe. This 

 distinction appears to be desirable inasmuch as in their 

 origin, structure and functions they are separate and 

 distinct bodies. 



Histology of the Pituitary Body. If a mesial 

 sagittal section be made through the pituitary it will 

 present an appearance which in a general way is the 

 same in many animals though the details vary some- SECTION "p'ra 

 what in each animal. In the monkey the arrangement ITARY BODY AND INFUN- 

 of the anatomic parts (Fig. 221) is similar to the ar- ^^TOTT*^?^ 

 rangement in man. It will be observed that the posterior tucut. a. Anterioi 

 lobe is solid and that there is no open connection with lobe. a'. A projection 

 the cavity of the third ventricle; that it is invested, over ^&SSSR 

 a large part of its surface, by a thin layer of epithelium. Posterior lobe connected 

 The anterior lobe, which lies in front of it is separated b y a stalk ih the in- 

 by a cleft which is the remnant of the cavity of the ffffSSk ctiasm.- 

 buccal pouch. Though the appearance of the ante- (Sckwalbefrom Quain.) 

 rior lobe, and the epithelial investment of the posterior 

 lobe is somewhat different, the latter is but a differentiation of the former, a 

 procedure that takes place in fetal life. The epithelial investment is 

 usually spoken of as the pars intermedia, and regarded histologically and 

 physiologically as a part of the posterior lobe. Superiorly the anterior lobe 

 and the pars intermedia are united, though a portion of the latter passes 

 upward and embraces, if it does not entirely surround, the infundibular 

 stalk; inferiorly and posteriorly the two bodies also unite. The posterior 

 surface of the posterior lobe is free from epithelial investment in the mid-line. 

 The extent to which the epithelium invests the posterior lobe varies in dif- 

 ferent animals. In the cat and dog it is almost complete. 



Microscopic examination of the anterior lobe shows the presence of 

 granular epithelial cells, the descendents of the original buccal epithelium, 



