62 THE PHYSIOLOGY OF THE ADRENALS. 



elements and most liable to occur in acute infectious and chronic 

 diseases and intoxications. 



2. By an indirect action upon the vascular supply of the or- 

 gans through a primary action upon the centers of the nervous 

 elements that control the adrenal secretion and most liable to occur 

 in acute intoxications by toxins, venoms, vegetable and mineral 

 poisons. 



That a simultaneous action upon both the suprarenal ele- 

 ments and the centers of their nervous supply may occur, how- 

 ever, is probable. 



3. The period between the two general stages, stimulation and 

 depression, seems to coincide with that considered in the course of 

 acute disease as the crisis. 



As toxic effects are alone involved in the foregoing proc- 

 esses, it is probable that: 



4. The adrenals are potent factors in the efforts of the or- 

 ganism to prevent the destructive effects which this selective affinity 

 engenders, when poisons, in sufficient doses to do harm, are intro- 

 duced into the circulation. This subject will again be considered 

 in the chapter on "Immunity." 



CHEMICO-PHYSIOLOGICAL PROPERTIES OF THE ADRENAL 

 SECRETION. 



Digitalis, notwithstanding its apparent predilection for the 

 heart, affects this organ through its action upon the adrenals. 

 But the heart-muscle is not alone stimulated by this drug; the 

 entire muscular system responds to its action precisely as it 

 does to that of other sufficiently active agents. Muscular over- 

 activity, tremors, increased response to electrical stimulation, 

 and other signs of erethism prevail. The vascular pressure is 

 raised to such an extent in the web of frogs and in the mesen- 

 tery of rabbits that the lumina -oi the arterioles are almost 

 completely obliterated. The heart's action is slowed and the 

 diastole prolonged, and when in the laboratory the behavior 

 of the ventricles can be watched, they actually become white 

 through the intensity of their contraction. That this is at- 

 tributable to the powerful contracting effect of suprarenal 

 extract upon muscular tissue and its constricting influence upon 

 vessels supplied with muscular fibers, as demonstrated by 



