THE ADRENAL SECRETION AND THE HEART. 



439 



supply. That the role of the coronary blood is precisely that 

 which obtains elsewhere in the organism is forcibly suggested 

 by the experiments of Langendorff, who was able, according to 

 Porter, "by circulating warmed oxygenated defibrinated blood 

 through the coronary vessels, to maintain the hearts of rabbits, 

 cats, and dogs in activity after their total extirpation from the 

 body." It is clear that the blood-plasma can incite functional 

 activity when introduced through the coronaries as well as when 

 introduced into the ventricles. "Even pieces removed from the 

 ventricle will contract for hours," continues the author, "if fed 

 with blood through a cannula in the branch of the coronary 

 artery which supplies them (Porter 16 ). It is evident, therefore, 

 that the cause of the rhythmic beat of the heart lies within the 

 heart itself, and not within the central nervous system." 



The italicized words represent precisely the factor of the 

 problem which must be eliminated to enable us to differentiate 

 the role of the coronary plasma from that of the Thebesian 

 plasma, for blood will not alone induce contraction of the car- 

 diac walls; almost any irritant will under appropriate condi- 

 tions. Indeed, in the latter case it will sometimes undergo con- 

 tractions without any external irritation; thus, "a strip of 

 muscle cut from the apex of the tortoise ventricle and suspended 

 in a moist chamber begins in a few hours to beat apparently 

 of its own accord with a regular, but slow, rhythm, which has 

 been seen to continue as long as thirty hours. If the strip is 

 cut into pieces and placed on moistened glass slides, each piece 

 will contract rhythmically. Yet in the apex of the heart no 

 nerve-cells have been found" (Porter). Hence the power to 

 contract is inherent in the contractile tissues, and subject, as 

 elsewhere in the organism, to exacerbations of activity under 

 appropriate stimulus. This fact being now established, our in- 

 quiry is simplified, since we need only to inquire into the nature 

 of the processes through which it is utilized. 



Analysis of the requirements of the right heart soon re- 

 veals the fact that the muscle-fibers require the same blood- 

 supply that any muscle of the body does. Indeed, we then 

 realize that the coronary arteries are their only source of oxy- 



16 Porter: Journal of Experimental Medicine, vol. ii, p. 391, 1897. 



