Structure of the Pituitary 



81 



granular in character rather than hyaline. In both cases the cells ultimately 

 break down, setting free the hyaline or granular substance. 



As has already been mentioned, the pars intermedia is by no means every- 

 where sharply marked off from the pars nervosa, for strands of the cells 

 of the pars intermedia may extend a variable distance between the fibres 

 of the pars nervosa. The hyaline and granular globules which have been 

 derived from its cells also pass into the substance of the pars nervosa and 



Fig. 52. — Portion of pars anterior of cat's pituitary, showing the groups of 

 oxyphil cells with vascular spaces between the groups. Several vesicles, 

 surrounded by cells, are included in the section. Magnified 400 diameters. 



are seen between its fibres : they can, in fact, be traced as far as the con- 

 tinuation of the third ventricle into the stalk. This fact was pointed out 

 by Herring, who concluded that the hyaline and granular substances which 

 are produced by conversion and breaking down of the cells of the pars 

 intermedia form the secretion of this portion of the pituitary, and that this 

 secretion passes into the cerebro-spinal fluid. In confirmation of Herring's 

 conclusion, evidence that the active principle of the posterior lobe of the 

 pituitary is present in cerebro-spinal fluid has been obtained by Cushing 

 and Goetsch, although their results have been traversed by Carlson. It 

 has, however, been shown by Cow that intravenous administration of 



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