104 MEDULLA 



An injection of 10 to 20 mgms. of morphine may elevate the 

 blood sugar to 250 milligrams per 100 cc. After exclusion of 

 the adrenals the blood sugar does not rise above 115 milligrams 

 per 100 cc. Hence in the cat, in which morphine is an ex- 

 citant, morphine produces a marked stimulation of epineph- 

 rine secretion. In the dog, in which (unlike in the cat) 

 morphine is not an excitant, this drug also increases epineph- 

 rine discharge, by central stimulation. However, the hyper- 

 glycemia which follows morphine injections in the dog is not 

 prevented by excluding the adrenals from the circulation. 



Histamine. The intravenous injection of 0.01 to 0.1 mgm. 

 of histamine into a cat, after excision of the superior cer- 

 vical ganglion causes dilatation of the pupils but not if the 

 adrenals have been excluded from the circulation. 147 This 

 effect is attributed to the discharge of epinephrine and may be 

 sufficiently great to prevent the capillary damage caused by 

 histamine. 457 



OTHER FACTORS AFFECTING THE SECRETION OF EPINEPHRINE 



Besides the instances cited above, many other conditions 

 and the injection of a variety of substances into the blood 

 stream result in an increased output of epinephrine. The 

 epinephrine store is thus a very labile and sensitive entity which 

 responds to numerous stimulants. 



Shock induced in unanesthetized dogs by injections of 

 peptone 657 is accompanied by an increased secretion of epineph- 

 rine. In anaphylactic shock 118,547 this increased secretion 

 is slight, for it does not result in a diminution of the epinephrine 

 content of the adrenals nor is the hyperglycemia of shock 

 absent in the adrenalectomized guinea pig. 



Many other substances when injected into the blood stream 

 cause reactions which indicate an increased discharge of epineph- 

 rine. Thus the hyperglycemia following injections of vari- 

 ous salts, which is slight after section of the splanchnics, is 

 attributed to epinephrine discharge. Mercury salts, arsenic, 



