THE PITUITARY BODY 



tuberalis. Extracts of the pars tuberalis may have some 

 pharmacological effects resembling those of the pars neu- 

 ralis. Quantitatively, however, these effects are much weaker 

 than those of the pars neuralis or the pars intermedia. Also, 

 it is not known to what extent the effects are due to the post- 

 mortem diffusion of the active principles of the pars neuralis. 

 On the other hand, some effects resembling those of pos- 

 terior-lobe extracts have been obtained by administering 

 extracts of the pars tuberalis and overlying tuber cinereum 

 after hypophysectomy. It must be admitted, therefore, that 

 observations in hypophysectomized animals do not exclude 

 the possibility that active principles resembling those ex- 

 tracted from the pars neuralis are vicariously secreted by the 

 tissues of the pars tuberahs and/or tuber cinereum. In ani- 

 mals hypophysectomized by an adequate technique, how- 

 ever, we can obtain information on the importance of the 

 pars neuralis and the pars intermedia. 



Krogh and Rehberg (1922) concluded that the vasomotor 

 system in the frog is unstable after hypophysectomy. Dila- 

 tation of the capillaries often followed by rapid transient 

 constriction or dilatation was observed. They were inclined 

 to believe that the effects were partly due to an absence of 

 the hormone maintaining the tone of the capillaries. (See also 

 the later work of Krogh [1929].) According to Orias (1934), 

 the blood pressure of toads {Bufo arenarum) i month after 

 operation is lower after total hypophysectomy than after 

 extirpation of the pars glandularis (control: 38 mm. Hg; 

 extirpation of the pars glandularis: 29 mm. Hg; hypophy- 

 sectomy: 17 mm. Hg). This difference can hardly be at- 

 tributed to the loss of the pars neuralis inasmuch as Orias 

 found that the blood pressure of hypophysectomized toads 

 was elevated to about equal levels by implants of either the 

 pars neuralis (50 mm. Hg) or the pars glandularis (46 mm. Hg) . 



The blood pressure of the mammal (dog) may be lower 

 after the removal of the pars glandularis but not after the 



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