776 PHYSIOLOGY OF DIGESTION AND SECRETION. 



celerated, while the blood-pressure is increased sometimes to an 

 extraordinary extent. These results are obtained with very small 

 doses of the extracts. Schaefer states that as little as 5J mgms. 

 of the dried gland may produce a maximal effect upon a dog weigh- 

 ing 10 kgms. The effects produced by such extracts are quite tem- 

 porary in character. In the course of a few minutes the blood- 

 pressure returns to normal, as also the heart beat, showing that the 

 substance has been destroyed in some way in the body, although 

 where or how this destruction occurs is not known. According to 

 Schaefer, the kidneys and the adrenals themselves are not respon- 

 sible for this prompt elimination or destruction of the active sub- 

 stance. Several observers* have shown satisfactorily that the ma- 

 terial producing this effect is present in perceptible quantities in 

 the blood of the adrenal vein, so that there can be but little doubt 

 that it is a distinct internal secretion of the adrenal. Dreyer has 

 shown, moreover, that the amount of this substance in the adrenal 

 blood is increased, judging from the physiological effects of its in- 

 jection, by stimulation of the splanchnic nerve. Since this result 

 was obtained independently of the amount of blood-flow through 

 the gland, Dreyer makes the justifiable assumption that the adrenals 

 possess secretory nerve fibers. Abelf has succeeded in isolating a 

 substance from the gland that produces the effect on blood-pressure 

 and heart rate, and proposes for it the name epinephrin hydrate, 

 He assigns to it the formula C 10 H 13 NO 3 . iH 2 and describes it as 

 a peculiar, unstable, basic body. Salts of epinephrin may be ob- 

 tained which when injected into the circulation cause the typical 

 effects produced by injection of extracts of the gland. 



Other crystalline products, adrenalin (C 9 H 13 NO 3 ), suprarenalin, 

 etc., have been prepared from the gland and show a most marked 

 influence in constricting the blood-vessels. These substances are 

 much used practically in minor surgical operations as a hemostatic 

 to check the flow of blood. The constriction of the blood-vessels 

 seems to be due to a direct effect upon the walls of the vessels, either 

 upon the musculature itself or upon the peripheral nerve fibers dis- 

 tributed to these muscles. That the effect is not entirely central 

 is indicated by the fact that after destruction of the vasoconstrictor 

 center and removal of the spinal cord injection of the extracts causes 

 a rise of blood-pressure of 100 per cent, or more. Langley has 

 called attention to the peculiar fact that adrenal extracts or so- 

 lutions of adrenalin do not act upon all varieties of plain muscle, 

 but only on those innervated by nerve fibers originating in the sym- 

 pathetic chain of ganglia. It has been proposed, therefore, to use 

 these solutions to determine whether or not given vascular areas, 



* " American Journal of Physiology, " 2, 203, 1899. 



t Abel, " Berichte d. deut. chem. Gesellschaft, " 37, 368, 1904. 



