THE NUTRITION OF THE HEART 163 



solution affects the rate of the beat, and the pressure affects its strength. 

 It is, however, obvious that in perfused preparations changes in pres- 

 sure are likely to cause alterations in rate as well as in force, unless 

 great care is taken to keep the heart itself as warm as the perfusion 

 fluid. 



The importance of an adequate pressure in the coronary vessels has 

 been clearly brought out in certain experiments in which the beat has 

 been maintained for a short time by establishing a pressure in the cor- 

 onary vessels by means of indifferent fluids or gases. Thus, if oxygen 

 gas is allowed to pass through the vessels under pressure, the heart will 

 beat for a short time, and the same result has been observed even when 

 mineral oil or mercury has been perfused under pressure (Sollmann). 



The necessity for an adequate oxygen supply is very readily demon- 

 strated. If the darker blood ejected from the right auricle with each 

 heartbeat is transferred immediately to the perfusion bottle, the heart- 

 beat will soon become feeble and irregular, to be readily restored to 

 normal when this dark blood is shaken up with air or oxygen. 



By artificial perfusion in the manner above described, the automatism 

 of the heart may be restored many hours after death. Partial restora- 

 tion, confined to the auricles or to that part of the ventricles lying im- 

 mediately adjacent to the large blood vessels, can also be accomplished 

 in the heart of man several days after death, provided death has not 

 been caused by some acute toxic infection such as diphtheria or septice- 

 mia. The Russian physiologist Kuliabko, has succeeded in restoring for 

 over an hour the normal beat of the heart of a three-months-old boy 

 twenty hours after death from double pneumonia, but here again the 

 pulsation returns only in certain parts of the heart. As will be pointed 

 out, the remarkable resistance of the heart muscle displayed in these 

 experiments has been taken as an argument in favor of the myogenic 

 hypothesis for automatic rhythmic power of cardiac muscle, the argu- 

 ment being that nervous structures could not live so long a time after 

 death. The fallacies in this argument are discussed elsewhere. 



Heart-Lung Preparation. Although the isolated heart is most useful 

 for the investigation of many of the functions of this organ, particularly 

 for the study of the effect of alterations in the chemical composition of the 

 perfusion fluid and the action of drugs, it is not so suitable when blood 

 instead of artificial plasma is to be perfused or when the effects of altera- 

 tions in the physical conditions of the inflowing or outflowing blood are 

 under investigation. In such cases it is better to use the heart-lung 

 preparation, which moreover has the added advantage that it requires 

 less blood, the proper aeration of which is affected through the lungs 

 (cf. 48 ). 



