VASOMOTOR REFLEXES 375 



less contracted blood-vessels, or possibly to the additional con- 

 traction of the blood-vessels of the small areas other than those 

 previously affected by the drug. 



But the comparison of the vasomotor reflexes before and after 

 the injection of adrenin ("adrenalin" Parke, Davis & Co.) seems 

 to show that the pressor reflex is slightly decreased in the latter 

 case. The results of Hoskins and Rowley were similar and 

 more definite. The elimination of the function of the supra- 

 renal glands by tying them off gave no clear results.* 



The injection of thyroidin (Parke, Davis & Co.) and the extir- 

 pation of both thyroid glands do not appear to have any distinct 

 influence upon vasomotor reflexes. 



Pituitrin (Parke, Davis & Co., surgical) showed scarcely any 

 significant results. 



All these experiments were performed on dogs under brain 

 compression for the purpose of excluding any influences from the 

 increased respiratory movements and those of anaesthetics and 

 other drugs. 



8. THE QUESTION AS TO WHICH VASCULAR AREAS ARE CON- 

 STRICTED OR DILATED ON CENTRAL STIMULATION OF 

 SOMATIC NERVES 



The fall of blood-pressure produced by stimulation of the de- 

 pressor nerve is effected chiefly by dilatation of the splanchnic 

 area,-i though, as Bayliss has shown, the vessels of the limbs, 

 head, and neck also partake in the relaxation. The latter 

 writer showed also that the rise of blood-pressure on stimula- 

 tion of the central stump of the splanchnic (?) nerve was, for 

 the most part, due to the constriction in the splanchnic area. 

 The reflex rise of blood-pressure due to the stimulation of the 



*That is to say, when the nerves to the limb are intact. In the denervated 

 limb there is a very important difference according to whether or no the ad- 

 renal bodies are eliminated. Mr. Pearlman and myself have recently found 

 that when the central end of the sciatic is stimulated in such a way as to give 

 a pressor response the intact limb follows passively the blood-pressure while the 

 denervated limb constricts. After removal of the adrenal bodies the dener- 

 vated limb also dilates. These results are explained more fully in a paper about 

 to be published in 'Endocrinology.' — S. V. 



