HYPOPHYSIS CEREBRI 



577 



earlier terminology (Flcsch/ 1880), which was based simply upon a 

 difference in the degree of tingibility, probably represent merely different 

 functional phases of the same cell type. The classification of the cells as 

 acidophils and basophils, a distinction based upon a more precise micro- 

 chemical difference, accords with a topographical segregation and more 

 probably designates an actual functional division. True chromophobes, 

 cells which stain only faintly and with difficulty in either acid or basic 

 dyes and probably functional phases of acidophil and basophil cells 

 appear first only in the higher sau- 

 ropsids (Tilney). The nuclei of 

 the several cell types are large and 

 deeply staining. The cells in great 

 part rest directly upon the endothe- 

 lial walls of the capillaries. The 

 blood-vessels are said to contain 

 colloid. 



Comparative histologic studies 

 indicate that the pituitary gland 

 has a twofold activity, one part de- 

 pendent upon the basophils, the 

 other upon the acidophils. The 

 residual lumen is lined only with 

 basophils, and occasionally contains 

 colloid. Comparative morphology 



indicates that the neural portion may represent an original special sense 

 organ. It has been suggested by Tilney (Mem. Wistar Inst., Biol. and 

 Anat., No. 2, 1911) that the basophils contribute their secretion by way 

 of the residual lumen and the infundibular process to the cerebrospinal 

 fluid, and the acidophils directly through the blood spaces. 



According to Dandy and Goetsch (Amer. Jour. Anat., 11, 2, 1911), 

 the pars distalis receives from eighteen to twenty small arteries which 

 converge to it from the circle of Willis. Within the lobe no true arteries 

 or veins occur. The blood channels are sinusoidal in nature; they drain 

 into a venous circle overlying the circle of Willis. 



The above description of the hypophysis is based largely upon dog 

 and cat material. Our knowledge of the human hypophysis is less 

 complete; but as far as is known, the structural elements are essentially 

 closely similar. 



The nerve supply to the hypophysis in the dog is, according to Dandy 

 (Amer. Jour. Aunt., l."i, :!, 1913), derived from the carotid plexus of the 



FIG. 495. PARS DISTALIS, HYPOPHY- 

 SIS OF CAT. (Tilney.) 



