Structure of the Pituitary 



83 



globules are greatly increased as the result of thyroidectomy (Herring). 

 Cushing states that this increase also results from extirpating the 

 pancreas, and that it occurs as the result of section of the infundi- 

 bular stalk. 



Pars nervosa (also known as the neuro-hypophysis or infundibular 

 body).— This is formed almost entirely of neuroglia fibres with neuroglia 

 cells scattered amongst them. Many of the fibres arise from these cells, 

 others from the ependyma cells of the infundibulum and of its extension 

 into the gland. Between the neuroglia fibres, especially in the neighbour- 





«a* 



.<*** *~ 



Fig. 55. — Section of posterior lobe of pituitary of cat, including a portion of the central 

 cavity which is continuous with the infundibulum of the third ventricle. (Herring.) 



a. ependyma of central cavity ; 6, colloid or hyaline matter in central cavity : some of it is seen passing 

 through the ependyma of the pars nervosa ; e, ependyma fibres ; d, hyaline masses; «, a granular 

 mass in pars nervosa. 



hood of the stalk, but also in other situations, is to be seen the hyaline and 

 granular matter already referred to; sometimes in the form of swollen 

 cells such as have been described in connexion with the pars inter- 

 media, sometime as amorphous masses ; these masses are traceable, as 

 already mentioned, to the infundibulum, where they may be seen passing 

 through the ependyma into the cavity of the ventricle (fig. 55). There can 

 be little doubt that the physiological activity of extracts of the pars nervosa 

 is connected with the presence of this substance within it, since extracts of 

 ordinary nervous and neuroglial substance have not the same action. Some 

 authors have described nerve-cells within the pars nervosa — but according 

 to Herring these do not occur, and there are very few nerve-fibres. The 

 pars nervosa is the least vascular portion of the pituitary, its blood-vessels 

 being comparatively few in number. 



