Histological Appearances of the Mammalian Pituitary Body 123 



posterior lobe of the mammalian pituitary in its early development 

 retains for a time a glandular structure. In the adult mammal the 

 epithehal investment of the posterior lobe is regarded by Kolliker as 

 the representative of an infundibular gland. B. Haller (14) states that 

 in mammals — as a type of which he takes the mouse — and in all other 

 classes of vertebrates the anterior lobe of the pituitary and epithelial 

 investment of the posterior lobe form a gland, the tubules of which open 

 by a small median and ventral mouth into the space between the pia and 

 dura mater. Haller believes that the pituitary in all vertebrates secretes 

 directly into the subdural space. Edinger (9) denies that this is true 

 of the human pituitary, Salzer (36) could find no opening in the pituitary 

 of the rat and mouse, and Sterzi (42) found none in the pituitary of 

 Petromyzon. 



There are other views on the structure and functions of the pituitaiy 

 body. Boeke (3) and Gemelli (11) describe appearances in the posterior 

 lobe of fishes which they regard as indicative of sense organs. Cyon (6) 

 looks upon it as an organ which regulates the amount of blood passing 

 to the brain. Guerrini (13) and others believe that the pituitary 

 produces a secretion which has a vague antitoxic action. 



Our knowledge of the structure of the pituitary body is, therefore, 

 far from exact, and is inadequate to account for the physiological effects 

 which follow intravenous injection of extracts, especially of the posterior 

 lobe. Even the important question as to whether the glandular portion 

 secretes directly into the subdural space is still unsettled. The work, the 

 results of which are given in this paper, was begun with the intention of 

 investigating the physiological histology of the posterior lobe, but the two 

 portions of the pituitary were found to be so closely associated that no 

 part would be complete without careful consideration of the other. The 

 development and comparative anatomy of the pituitary body have been 

 examined, but are only touched upon in this paper where reference to them 

 throws light upon the particular point considered. 



Material axd Methods Employed. 



The cat furnishes some of the best material for the study of the pituitarj^ 

 bodj^ for in this animal the posterior lobe retains throughout life its 

 original cavity in free communication with the third ventricle of the brain. 

 The structure of the posterior lobe in the cat is thus rendered simpler 

 because the arrangement of the cells which line the cavity persists in the 

 adult in much the same manner as obtains in the developing organ. The 

 parts which are derived from the buccal mucous membrane form an almost 

 complete investment for the nervous portion, and the original lumen of 

 the epithelial pouch also persists throughout life in the form of a well- 

 marked cleft. The so-calle*d colloid cysts are also prominent features in 

 the pituitary of the cat. 



