204 E. G. HOSKINS 



able block in the pulmonary blood-stream may interfere with the adequate 

 filling of the left side of the heart and hence cause diminution of sys- 

 temic blood-pressure. 



Earlier researches having definitely shown that epinephrin is capable 

 of evoking either vasodilator or vasoconstrictor effects, it became im- 

 portant to determine how and to what extent these effects are associated 

 in a composite reaction to the drug. Hartman, in 1915, subjected the 

 problem to direct study. 



His experiments were made upon cats. Urethane, was the anesthetic 

 used throughout. The epinephrin was administered by jugular vein 

 in concentration of 1:100,000. In most cases injections of 0.2 c.c. were 

 made at a uniform rate in each instance over a period of from fifteen to 

 thirty seconds. Blood-pressure was registered from the carotid artery. 



In the first series of experiments the circulation was confined to the 

 extra-splanchnic vessels. This was brought about by ligating the inferior 

 and superior mesentery arteries, the celiac axis, and sometimes also 

 the renal arteries. Of 23 animals thus prepared, 14 showed a distinct 

 fall of arterial pressure after injection of the standard dose of epinephrin. 

 In 4 animals in which there had been a preliminary rise of pressure fol- 

 lowed by a fall, the same close failed to cause a rise after the splanchnic 

 vessels had been occluded. In two instances in which, previous to the liga- 

 tion of the splanchnic vessels, a rise of pressure alone was obtained, after 

 the ligation, only a fall was produced. In another instance, a depressor 

 effect of 14 per cent was increased to 32 per cent by occlusion of the 

 splanchnic vessels. From these experiments Hartman drew the correct 

 conclusion that small doses of epinephrin bring about relaxation of the 

 "peripheral arteries." In no case was evidence of constriction observed. 

 No attempt was made in this study to differentiate the effects in the various 

 "peripheral" structures involved. 



In a second series of observations the circulation was confined to a 

 considerable extent to the splanchnic area. Ligatures were placed about 

 the abdominal aorta above the iliac arteries, about both subclavians and 

 both carotids. Thus, in addition to the splanchnic circulation, there re- 

 mained that of the trunk and the thoracic viscera. Observations were 

 carried out on 20 animals, using the same standard dose of epinephrin, 

 administered in the same way as in the preceding series. In all but 2 of 

 the 20 cases this standard dose caused only a rise of arterial pressure, an 

 effect just the opposite of that caused by the same dosage before the ves- 

 sels were occluded. An exception to this general statement is that immedi- 

 ately after the occlusion, while the blood-pressure was abnormally high, 

 depressor effects were sometimes seen, but later, as the pressure decreased, 

 the fall was converted to a rise. As the pressure decreased below normal 

 the percentage rise from the standard dose usually increased. 



In 4 animals the two types of experiment were combined, both splanch- 



