576 



THE DUCTLESS GLANDS ENDOCRIN GLANDS 



FIG. 493. PARS TUBERALIS, HYPO- 

 PHYSIS OF CAT (Tilney.) 



(a) Pars hibrrtilix. The cells of this portion are arranged in large 



tubular acini; the lumina may contain colloidal material. The cells 



are of the cuboidal type, sometimes ciliated, frequently two layers deep. 



The cytoplasm of the cells is sparse, 

 homogeneous and deeply basophilic. 

 The nuclei are large and vesicular. 

 Blood-vessels (sinusoidal capillaries) 

 are numerous, and are said occa- 

 sionally to contain colloid. 



(b) Pars infundibularis. Here 

 the cells are arranged in a dense 

 stratum several layers deep. Occa- 

 sional acini (cysts) occur, but they 

 are smaller than in the pars tuber- 

 alis and are lined with only a sin- 

 gle layer of low cuboidal cells. 

 These cells contain large vesicular 

 centric nuclei surrounded by a con- 

 siderable layer of faintly basophilic 



granular cytoplasm. Blood-vessels are very meager and thin-walled. 

 (2) Pars distal is. This portion is surrounded by a robust fibrous 



capsule continuous posteriorly with a thinner investment for the neural 



lobe. Delicate trabeculas traverse 



the parenchyma and support the 



very abundant plexus of arterio- 



venous sinusoidal blood spaces. The 



peripheral cells of the pars distalis 



constitute a narrow zone of almost 

 exclusively basoi>lii/ic cells. The 

 cells of the main central portion are 

 arranged in dense convoluted anas- 

 tomosing cords. The cords com- 

 prise axial and parietal cells. The 

 parietal cells are the larger, of 

 polygonal shape, and with a gran- 

 ular cytoplasm deeply acidophilic. 

 These are the 'eosinophilic' or udd- 

 o/i/ii/ic ('chromophil') cells. The axial cells are smaller; their cyto- 

 plasm contains 'neiitrophilic' granules. These are the 'chief,' or 'chrom- 

 ophobe' cells. The so-called 'chromophils' and 'chromophobes' of the 





FIG. 494. PARS INFUNDIBULARIS, HY- 

 POPHYSIS OF CAT. (Tilney.) 



