200 K. G. HOSKINS 



any noteworthy change in the pulse-rate or pulse-pressure, hence was 

 ascribed to primary vasodilatation. By properly graduating the dosage, 

 it was found possible to elicit additive depressor effects by successive doses 

 and by increasing these to a critical point to shift the reaction to the pres- 

 sor side and to obtain additive pressor effects. Pithing the brain and 

 upper cord caused a fall in the blood-pressure level ; at this lower level 

 doses of epinephrin which previously had given depressor effects now 

 caused only increase of pressure. There was no detectable alteration in 

 heart action which could account for the reversal, hence it was inferred that 

 pithing had converted the vasodilator to a vasoconstrictor response. Sim- 



i t i i i urn i i i u i i ru I n 



. c.c. .SSc.c. .1 c.c. .06 c.c. 



Fig. 2. Graph showing graduated depressor reactions due to varying doses of 

 epinephrin in cats. Intravenous injections 1:100,000 solution (0.3, 0.2, 0.1 and 0.05 

 c.c.) given at the rate of 0.01 c.c. per second. Time, half-minutes. (After Cannon & 

 Lyman, Am. J. Physiol.) 



ilarly, the reverse of reaction could be obtained by lowering the blood-pres- 

 sure either through stimulation of the depressor nerve or injection of 

 nitroglycerin. From a consideration of all of the available evidence, the 

 conclusion was reached that epinephrin vasodepression is not of central 

 origin, is not due to blocking of vasconstrictor impulses, nor to stimulation 

 of supposed vasodilator sympathetic nerve endings. The differential ef- 

 fects were tentatively ascribed to varying reactions of the smooth muscle 

 according to its relative state of tonus. It is tempting, in this connection, 

 to apply Verworn's theory of inhibition, namely, that it is due merely 

 to subminimal stimulation qualitatively similar to that producing activity. 

 Hartman in 1015 again studied the depressor effects of epinephrin. 

 Of 49 normal cats only 1 failed to give a fall in pressure following the 

 administration of a small standard dose of epinephrin. In one interest- 

 ing experiment the standard dose of epinephrin gave a fall in pressure 

 from an initial level of 102 mm. After hemorrhage, which reduced the 



