AUTOMATIC REGULATION OF THE HEART. 95 



artery into the mouth of a coronary artery. Injections of various substances 

 capable of causing occlusion have also been tried. 



In 1867, v. Bezold noted in rabbits after clamping off the coronary 

 artery that the heart-beat grew rapidly smaller and smaller; then 

 the contractions occurred in groups, periodically; later on the regular 

 movement of the ventricle ceased entirely, and in its place the muscle- 

 wall exhibited a peculiar fibrillary contraction; finally the heart stood 

 still. As the circulation was reestablished after removal of the clamp, 

 the phenomena appeared in reverse order until the heart regained its 

 normal beat. 



If in a dog the right descending coronary artery and the circumflex 

 artery, together with the artery of the septum, are occluded, the heart 

 soon ceases to beat. The closure of only two of the three arteries caused 

 a cessation of contraction in 9 out of 14 animals; while closure of the 

 septal artery or of the right coronary artery alone had no effect. In 

 almost all instances the auricles likewise cease beating. The heart of 

 a dog that has once ceased to beat recovers only with great difficulty. 

 It appears that the fibrillary contractions are due to irritative injury in- 

 flicted during the operation, and not alone to the stasis of the blood. 



If in rabbits only the left coronary artery is occluded the beat of the 

 left heart is slowed and weakened, while the right heart pulsates without 

 change. As a result it occurs that the left half of the heart can no longer 

 empty itself completely, so that particularly the left auricle becomes 

 filled to distention with blood, while at the same time the unaffected 

 right heart continues to drive blood into the lungs. In consequence 

 edema of the lungs develops as a result of the high pressure in the 

 lesser circulation which is transmitted from the right heart through the 

 pulmonary vessels into the left auricle. According to Sig. Mayer 

 persistent dyspnea has a similar effect, with earlier weakening of the left 

 than of the right ventricle; the pulmonary edema preceding death can 

 be explained in this manner. 



The heart in the higher animals can maintain its activity only when 

 the circulation of blood through its walls is maintained. The heart 

 from which the blood is completely removed rapidly ceases to con- 

 tract. The coronary circulation must convey the necessary oxygen 

 and nutritive materials to the myocardium, as well as remove the 

 metabolic products from it. The excised "isolated" mammalian heart, 

 which is fed at body-heat through the coronary vessels with bright-red 

 blood, remains active. 



Langendorff maintains the circulation in the isolated heart by allowing the 

 coronary arteries to be filled from the aorta. Other fluids, for example, lake- 

 colored blood or serum, are incapable of maintaining the heart's activity. At 

 most, such solutions (as, for example, alkaline salt-solution mixed with egg-albu- 

 min 1000 albumin diluted with water, o.i sodium chlorid, o.i calcium chlorid, 

 0.075 potassium chlorid), in so far as they exert a slightly irritating effect, are 

 capable of stimulating the heart for a time. If the heart is placed in pure 

 oxygen the pulsation may be maintained for a considerable time by passing 

 serum through the cardiac vessels. 



Also the isolated frog's heart can be included in a circulation by 

 means of suitable tubes. To maintain its contractions oxygen and 

 nutritive fluid are necessary to distend its cavities. This object is 

 best fulfilled by arterial blood; indifferent fluids (0.6 percent, sodium 

 chlorid) quickly bring about a condition of "apparent death," from 

 which, however, the organ can be revived by nutritive fluids. 



