EFFECTS OF SECRETION ON THE HEART AND VESSELS. 



15 



are not endowed with a vasomotor supply, we find that they 

 nevertheless contract under the influence of suprarenal extract. 

 Szymonowicz 48 observed that the pressure rose and fell in the 

 external jugular vein, along with the pressure caused in the 

 arteries by injections of this substance. Auld, 49 in the course 

 of a series of experiments which had in view the influence of 

 suprarenal extract on the blood, states that when it was in- 

 jected into a vein "which had been clamped as high up as prac- 

 ticable, on releasing the vein after a few minutes a marked 

 diminution of pressure was recorded as compared with that 

 produced by injection into the free vein." While it is difficult 

 to account for the general increase of vascular pressure caused 

 by the extract without including vasomotor nerves in the 

 process, a direct action upon the vascular muscles themselves 

 might underlie the result attained: a question which can only 

 be elucidated by stripping the vessels of all their nervous con- 

 nections and then watching the effects of the extract. This 

 procedure has been resorted to by Oliver and Schiifer, 50 and 

 these physiologists have shown that a vessel will contract after 

 all the nerves to it are cut. Even a freshly-excised vessel 

 one, therefore, obviously freed of all nervous influence will 

 respond to the contracting effects of an aqueous solution of 

 suprarenal extract, and, if a large vessel be used for the ex- 

 periment to render the change of caliber more appreciable, the 

 diameter will be found reduced nearly one-sixth. Furthermore, 

 these investigators 51 have found that it acts directly on the 

 muscles of the blood-vessels, and that this action occurs equally 

 well after section of the cord. As we have seen, destruction of 

 the adrenals or annihilation of their functions is followed by 

 extreme muscular weakness; this normally led them to the 

 conclusion that all varieties of muscle the striated, non- 

 striated, and the cardiac muscle (which histologically partakes 

 of both kinds of muscular tissue) are stimulated by the ex- 

 tract. Having further observed that the blood-pressure in- 

 creased rapidly, giving a steep rise to the kymograph-curve, 



48 Szymonowicz: Archiv fiir die gesam. Physiol., Bd. Ixiv, 1896. 

 "Auld: British Medical Journal, June 3, 1899. 

 60 Oliver and Schafer: Journal of Physiology, vol. xviii, p. 426. 

 Ibid., p. 230. 



