162 



Historical. 



The pituitary body was at one time tliought to be wholly derived from 

 the brain, but Rathke (26) in 1838 described the invagination of mucous 

 membrane which is now known as Rathke's pouch. Rathke rightly 

 assigned to this pouch the origin of the epithelial portion of the pituitary, 

 but was mistaken in believing it to be derived from the entoderm of the 

 fore-o-ut. His view was not at once accepted. Reichert (28) failed to find 

 the invagination, and put forward the theory that the epithelial portion of 

 the pituitary is a structure of mesodermic origin derived from the anterior 

 end of the notochord. His (14) lent additional support to Re i chert's view, 

 but made no special investigations of the subject himself. Both Rathke 

 (27) and Reichert (29) subsequently changed their opinions, the latter 

 believing the anterior lobe to arise from a proliferation of the cells of the 

 pia mater. Dursy (8) sought to unite the original view of Rathke with 

 that of Reichert and His, and described the origin of the epithelium of 

 the pituitary from the fore-gut, and the origin of its vascular stroma from 

 the tissue of the head of the notochord. W. Miiller (23) demonstrated 

 that the anterior lobe of the pituitary is derived from Rathke's pouch, 

 but fell into the same error as Rathke and Dursy in believing it 

 to be of entodermic origin. The later researches of Gotte (12) and 

 Balfour (3) showed that the pouch described by Rathke is derived, not 

 from the fore-gut, but from the epithelium of the buccal cavity imme- 

 diately in front of the oral plate. The pouch is now recognised as an 

 ectodermic structure. 



The posterior lobe of the pituitary was at first believed to represent the 

 anterior extremity of the brain (v. Baer (2)). Gotte (12) showed that in 

 amphibians this is not the case, the infundibulum being a later formation. 

 The researches of Mihalkovics (21), van Wijhe (35), Kupffer (20), and 

 others have demonstrated that the infundibulum cannot be regarded as the 

 representative of the anterior end of the brain axis ; it is an outgrowth 

 of the "Zwischenhirn" or thalamencephalon. 



The proximity of the anterior end of the notochord to the developing 

 pituitary body led to the belief, not only that the notochord enters into the 

 structure of the pituitary, but that it also exercises a mechanical influence 

 upon the formation of the infundibulum. Both His and Dursy considered 

 that a close union between the notochord and the wall of the cerebral 

 vesicle is the dominating factor in the development of the infundibulum, 

 but were not agreed as to the exact manner in which this is brought about. 

 W. M tiller believed that the head of the notochord anchors a portion of the 

 wall of the brain, and that with the growth of the surrounding tissues the 

 rest of the brain is carried forwards, leaving a diverticulum of its wall, the 

 infundibulum, attached to the notochord. The attachment is subsequently 

 dissolved b}^ a proliferation of connective tissue cells. Mihalkovics (21) 

 and others showed that the head of the notochord does not come into 



