, THE CIRCULATION OF THE BLOOD 297 



The results of direct experimental investigations of Porter, however, lead to 

 the conclusion that the existence of vaso-motor (constrictor) fibers for the 

 coronary arteries is highly probable. 



These investigations have been corroborated by the investigations of 

 Barbour and Prince who have found that when isolated monkey hearts are 

 perfused with autogenous hirudin blood diluted with Locke's solution con- 

 taining minute doses of epinephrin, the coronary flow is decreased. From 

 previous experiments on rings of the coronary artery of the human heart 

 the conclusion is drawn, that in man and the monkey, epinephrin constricts 

 the coronary arteries even though it dilates them in the dog, cat, rabbit, 

 and other animals. From these result the further conclusion is drawn that 

 in man and monkeys the coronary arteries are supplied with vaso-constrictor 

 nerves of true sympathetic (thoracico-lumbar) origin. 



The Effects of Ligation of the Coronary Arteries. As stated in a 

 foregoing paragraph the nutrition of the heart-muscle, its irritability and 

 contractility, depend on the blood-supply derived from the coronary vessels. 

 This is shown by the effects which follow its withdrawal. Ligation of both 

 coronary arteries in the dog is followed by a diminution in the force and 

 frequency of the heart-beat, and in a few minutes by complete cessation. 

 Ligation of even a single branch of a coronary artery of the dog heart, pro- 

 vided it supply a sufficiently large territory e.g., the arteria circumflexa 

 is sufficient to cause arrest in at least 80 per cent, of animals (Porter). With 

 the ligation of this vessel there occurs a gradual diminution in the force and 

 frequency of the systole until the heart comes to rest in diastole. All 

 the results which follow ligation are to be attributed in the light of experi- 

 ment to the sudden anemia which is thus established. The removal of the 

 ligature within a limited period and the return of the blood will restore 

 the nutrition and re-establish coordinate contractions. 



Fibrillary Contraction. In the decline in the frequency and force of the 

 systole consequent to the occlusion of the coronary arteries, it frequently 

 happens that as the coordinate contractions of the ventricles disappear, 

 they are succeeded by a series of independent contractions of groups of 

 muscle fibers to which the term fibrillary contraction has been applied. 

 With the establishment of this condition the surface of the heart presents 

 a peculiar twitching, flickering appearance, which continues for a variable 

 period, perhaps as long as the irritability persists at a sufficiently high 

 level. Though this result is to be attributed to the sudden anemia which 

 is thus established, the change in the heart musculature which gives rise 

 to the fibrillary contractions, is not clearly understood. It is possible 

 that the independent contractions of fibers and groups of fibers are the 

 result of an interference with the normal conductivity, or to a change in 

 the irritability. A similar condition may be established by stimulation 

 of the surface of the heart with rapidly repeated induced electric currents. 

 The excised heart of the mammal which has passed into the condition 

 of fibrillary contraction may be again made to beat rhythmically and 

 vigorously by first cooling it with normal saline, and then perfusing it 

 with warm defibrinated blood through the coronary vessels under a 

 suitable pressure. The same result can be brought about by first perfusing 

 it with a i per cent, solution of potassium chlorid until the heart comes 



