CHAPTER XVIII 

 THE NUTRITION OF THE HEART 



IN the lower vertebrates, such as the frog, the heart is directly 

 nourished by the blood which fills the cavities in its sponge-like struc- 

 ture. In the warm-blooded vertebrates, there is a special arrange- 

 ment of coronary vessels. The two coronary arteries' (right and left) 

 originate at the root of the aorta from bulgings of the aortic walls 

 the sinuses of Valsalva. The sinuses are three in number, corre- 

 sponding to the number of cusps of the semilunar valves. The 

 right coronary artery arises from the anterior sinus, the left coronary 

 artery from the left posterior sinus. Their branches penetrate the 

 muscular substance, and end in a rich plexus of capillaries. From 

 these arise the radicles of the coronary veins, which open into the 

 right auricle by the coronary sinus and other small veins. These 

 openings are valved by remnants of the primitive sinus venosus. The 

 heart, in contracting, exerts a greater pressure than that of the 

 coronary arteries, and so arrests the flow in these during the height 

 of systole, and squeezes the blood within the coronary capillaries 

 and veins on into the right auricle. On diastole, the coronary system 

 fills again. Sudden occlusion e.g., by the injection of paraffin of 

 any large part of the coronary arteries produces irregular and inco- 

 ordinate contractions " fibrillation," as it is called followed by 

 death of the heart. Degeneration of the coronary arteries in advanced 

 life is associated with a distressing form of cardiac illness known as 

 '' angina pectoris."' The great anatomist John Hunter, who died 

 after a heated debate, was found by Jenner to have calcified coronary 

 arteries. 



It has long been known that the heart of the frog or tortoise can 

 be kept beating normally for hours after removal from the body, 

 particularly if it is provided with a suitable solution of salts. Ringer 

 worked out the necessary ingredients of this solution to be : sodium 

 chloride, 0-7 per cent.; potassium chloride, 0-03 per cent.; calcium 

 chloride, 0-025 per cent. 



The excised mammalian heart can be kept beating in the same 

 way, provided the nutritive fluid is oxygenated and the heart kept 

 at body temperature. A solution containing one-third defibrinated 

 blood and two-thirds Ringer's salt solution is especially suitable. 

 The beat of the heart of a child was restored thereby twenty hours 

 after death from pneumonia; the excised heart of a cat was kept 

 beating for four days: the heart of a monkey was restored after 



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