14 THE PHYSIOLOGY OF THE ADRENALS. 



134 the second, and from 24 to 124 the third time, the interval 

 between the injections of extract and the highest-pressure 

 marks ranging from fifteen to thirty seconds. 



These experiments, to which others of a similar kind 

 could be added, speak for themselves. They distinctly show 

 that the inhibitory centers are not directly stimulated ~by the supra- 

 renal extract, as thought by Cybulski, Wallace and Mogt, Man- 

 kowsky, Gottlieb, and other careful observers. 



And, indeed, their conclusion is apparently justified, if 

 removal of the medulla and cord is left out of consideration, 

 and with injections of suprarenal extract as an only guide. In 

 other words, to the question does suprarenal extract directly 

 affect the cardio-inhibitory centers? an affirmative experi- 

 mental result on injecting it into mammals slowing of the 

 heart would always be obtained, while the crucial test sec- 

 tion of the vagus would at once confirm the conclusions pre- 

 viously reached by causing great increase in the rapidity of 

 the heart's action. But removal of the vagal centers and the 

 cord in no way preventing the action of the extract, the only 

 logical deduction that imposes itself is that the suprarenal ex- 

 tract exercises a stimulating action directly upon the cardiac 

 muscle. 



THE ADRENAL SECRETION AND THE VASOMOTOR SYSTEM. 

 The last deduction submitted necessarily implicates other 

 phases of the question. Prominent among these is the effect 

 ascribed to suprarenal extract upon the vasomotor system by 

 various physiologists and clinicians. Is there any such action? 

 Veins which are but little, if at all, influenced by the cardiac 

 impulse in respect to their rhythmical changes of caliber, the 

 blood before reaching them having to penetrate the capillary 

 system are distinctly contractile. This may be clearly seen 

 by examining the larger veins, especially those near the heart, 

 in bats' wings. While, to use Foster's 47 words, "similar rhyth- 

 mical variations, also possibly due to rhythmical contractions, 

 but possibly also of an entirely passive nature, have been ob- 

 served, very little is known of any nervous arrangements gov- 

 erning the veins." Granting, for the time being, that veins 



47 Foster: "Text-book of Physiology," 1895. 



