Effects of Intravenous Injection of Suprarenal Extracts 59 

 arteries. Along with the vascular contraction a slowing of the heart's 



O C7 



action (or even complete stoppage of auricular beats) may occur, due to an 

 effect on the cardio-inhibitory centre, and this may somewhat limit the rise 

 of blood-pressure (fig. 35). But if the vagi are cut or paralysed by atropine, 

 the heart-beats become enormously accelerated and also augmented in force 

 (primarily by the action of the autacoid on the auricles, but also somewhat 

 on the ventricles), 1 and this greatly increases the rise of blood-pressure 

 (fig. 36). There is some diminution in the depth of the respirations, and 





FIG. 35. Effect upon heart and blood -pressure of injecting suprarenal extract into a vein, with 

 vagi intact (dog). (This figure, as well as figs. 36 and 38, are from Oliver and Schafer, 

 Journ. Physiol., 1895, vol. xviii.) 



A, ventricle ; B, auricle ; C, arterial pressure ; D, signal ; E, time-marking in seconds. The tracings in this and 

 the next three figures have been reduced to rather less than half the size of the originals. 



occasionally a temporary cessation of breathing, especially in the rabbit. 2 

 But this disappears long before the effect on the blood-vessels has ceased 

 to show itself. The effect upon the vessels lasts a few minutes, gradually 

 passing off; after its passage the blood -pressure is usually a little lower than 

 before. The arteries which are most affected are those of the splanchnic 

 area (fig. 37) : those of the limbs and trunk rather less, although the 

 cutaneous vessels are usually strongly contracted : those of the pulmonary 

 system and of the brain only very slightly if at all, while those of the 

 coronary circulation are unaffected : indeed, in some animals these last are 



1 In birds, as Noel Paton has shown, the augmentation is confined to the auricles. 



2 Garrelon and Langloi* find that in the dog either diminution or increase of respirations 

 may occur, these effects depending upon the condition of the respiratory centre at the time. 



