THE PITUITARY BODY 



in the femoral artery and vein is diminished for about 90 

 minutes after the injection of the vasopressor principle into 

 the normal dog. The injection of the oxytocic principle is 

 followed by no change (Ceiling, Herri ck, and Essex, 1934). 

 It is agreed that the pressure within the portal vein falls 

 after the injection of posterior-lobe extract; however, the 

 interpretation of this effect varies (Clark, 1928; Holtz, 1932; 

 and McMichael, 1932). 



According to Meyenburg and Schiirch (1923), arterio- 

 sclerotic changes may appear in the aorta of rabbits into 

 which a posterior-lobe extract has been repeatedly injected 

 intravenously. Moehlig (1930) believed that such changes 

 occur oftener if the animals receive a high-fat diet. 



The intravenous injection of a posterior-lobe extract into 

 the bird produces a fall in the blood pressure (Paton and 

 Watson). In the fowl and duck it has been shown that this 

 change is due to the oxytocic principle and not to the vaso- 

 pressor principle or to substances like choline, acetylcholine 

 or histamine (Gaddum, 1928; Morash and Gibbs, 1929; and 

 Dietel, 1934). According to Gruber and Kountz (1930), the 

 oxytocic principle causes a dilatation of the coronary vessels 

 of the isolated rabbit's heart. 



The effects of posterior-lobe extracts on the capillaries of 

 the frog have been described by Krogh and Rehberg (1922), 

 Killian (1925), and Krogh (1929). Hogben and Schlapp 

 (1924) found that enormous doses of posterior-lobe extract 

 were required to produce a rise in blood pressure in the frog. 

 The prominent effect on the blood pressure of the tortoise 

 was found to be depressor. The vasopressor hormone has 

 no clear-cut effect on the branchial vessels of the eel, Anguilla 

 vulgaris (Keys and Bateman, 1932). 



In the intact animal the vasoconstrictor effects of a 

 posterior-lobe extract are not the same in different tissues. 

 In the cat, for example, the effects on the vessels of the 

 intestines are more marked than those on the vessels of 



[340] 



