EFFECTS OF EXTRACTS OF PARS NEURALIS 



tone" may prevent the cardiac effects (presumably due to 

 coronary constriction); phenobarbital ("Luminal"), on the 

 other hand, may have the opposite effect. Depending upon 

 experimental conditions, the injection of epinephrin may 

 favor or oppose the vasoconstricting effect of the vasopressor 

 principle on the coronary arteries (Melville, 1933; Antopol 

 and Rossler, 1934). Under appropriate conditions ephedrine, 

 histamine, morphine, nitrites, and papaverine have all been 

 found to lessen or prevent the adverse effects of the vaso- 

 pressor principle on the heart of normal or anesthetized 

 animals; in every case the investigator has considered that 

 the drug caused a dilatation of the coronary arteries, thus 

 opposing the constrictor effect of the posterior-lobe extract. 

 The phenomenon of tachyphylaxis can be observed in the 

 coronary arteries as in other arteries.'' 



The feeding of thyroid extract has been found markedly 

 to increase the toxic effect of posterior-lobe extract on the 

 heart (Clark, 1929; Appel, 193^). 



Apparently carotid-sinus reflexes play no important part 

 in the circulatory effects of the vasopressor principle. 

 Changes in the respiratory movements are usually attributed 

 to local circulatory changes in the respiratory center (Shar- 

 pey-Schafer and Macdonald, 1926; Gruber and Kountz, 



1930)- 



An account of some of the effects of posterior-lobe extracts 

 on the pulmonary circulation will be found in the reports of 

 Sharpey-Schafer and Macdonald (1926) and Holtz (1932). 



The blood flow in the carotid artery and jugular vein and 



^ The heart has been investigated in the cat, dog, and rabbit. In some experi- 

 ments the isolated heart (terrapin, rat, rabbit, and cat) has been used: Smith, 

 Miller, and Graber (1925); Gruber (1926); Hausler (1929); Mautner and Pick 

 (1929); Raginsky, Ross, and Stehle (1930); Ross, Dreyer, and Stehle (1930); Golden- 

 berg and Rothberger (1931); Melville and Stehle (1931); and Raginsky and Stehle 

 (193^-). 



The minute-volume output of the human heart before and after the injection of 

 posterior-lobe extract has been studied by Grollman and Geiling (1932) and Hartl 

 (1933)- 



[339] 



