HISTOLOGY OF THE POSTERIOR PITUITARY. 499 



basal end is shrouded in a blackened aggregation of cellular 

 masses, their histological origin must remain a matter of some 

 uncertainty." 



If, with these histological data before us, we examine 

 Plate I, a suggestive fact asserts itself: i.e., that the lamina 

 of ependymal cells referred to forms a skull-cap-like covering 

 for the second, or secretory, portion of the posterior lobe. The 

 glandular alveoli of the latter, with their colloid substance, 

 are, therefore, in the best possible position for the reception 

 of any nervous impulse that the ependymal cells may be able 

 to transmit outwardly. This is emphasized in Plate I, which 

 shows that this layer exactly covers the entire surface of the 

 secretory region without reaching beyond its limits. The se- 

 cretory region of the posterior lobe thus seems to be held in 

 the grasp, as it were, of its ependymal covering, which in turn 

 contains the nervous, "rather thick, varicose threads." This 

 suggests that the capsule may not be the insignificant structure 

 it is now thought to be. Even the fragmentary data we have 

 concerning it tend to indicate that it plays an important role 

 in the functions of the organ. 



Mere protective structures are usually detached without 

 much difficulty from the underlying tissues; Berkley states, 

 referring to the posterior body: "This lobe is so strongly ad- 

 herent to the dura that it pulls out of the rest of the pituitary 

 body in removing this with the brain, unless the membrane 

 is dissected with it from the base of the skull." Since the 

 capsule is the part of the lobe so strongly connected with the 

 dura, it must as firmly adhere to the layer of ependymal cells 

 beneath; otherwise efforts at removal would tear it away from 

 the latter. This firm hold of the capsule on the cellular layer 

 is fully accounted for by the thin, fibrous partitions the former 

 sends through the latter, but this in itself suggests an intimate 

 relationship between capsule and cellular layer, especially since 

 the "blackened aggregation of cellular masses," referred to 

 by Berkley, which form the basal extremities of the nervous 

 "threads," all terminate in what appears to be, in his draw- 

 ings, thickenings in the capsule proper. That such a relation- 

 ship between the capsule and the nervous elements must exist 

 is further shown by his reference, in the descriptive text of the 



32 



