954 INFLUENCE OF DUCTLESS GLANDS ON METABOLISM. 



and the heart is therefore still in connection with the cardio-inhibitory 

 centre in the medulla oblongata, the action of suprarenal extract is to 

 slow, and even to entirely stop, the contractions of the auricle. Under 

 these circumstances the ventricle continues beating with an independent 

 slow rhythm (Fig. 88). The result is to cause the pulse to be very 

 slow. On the other hand, when the vagi are cut or their cardiac ends 

 paralysed by atr opine, the effect upon the heart is precisely the reverse 

 (Fig. 89). The strength and frequency of the auricular contractions 

 are markedly increased, and those of the ventricle are correspond- 

 ingly augmented. This naturally has the effect of sending a vastly 

 greater amount of blood into the arteries, which by itself would alone 

 produce a great rise in the arterial pressure. The direct action upon 



FIG. 90. Effect of suprarenal extract upon heart, limb, spleen, and blood pressure, after 

 section of cord and vagi. The forearm in this experiment was at first passively 

 expanded, but its contraction is afterwards manifest. (Reduced to one-half.) 



the arteries is, however, quite as marked as that upon the heart. 

 If the blood pressure be taken in a dog in the usual way, by connect- 

 ing a mercurial manometer with the femoral artery, and if a minute 

 dose of suprarenal extract be now injected into a vein, it is found that 

 even with the vagi uncut, and the heart therefore slowed by the action 

 of the extract, the blood pressure rises considerably (Fig. 88). But 

 with the vagi cut or paralysed by atropine the rise can only be 

 characterised as enormous (Fig. 89). 



The contraction of the arteries is further exemplified by the fact that 

 if an organ, such as a limb or the kidney or the spleen, be enclosed within 



