CIRCULA TJOJY. 1 83 



ligations Porter observed not a single arrest in consequence of laying the 

 artery bare and placing the ligature ready to be drawn, the only effect of the 

 mechanical procedure being an occasional slight irregularity in force. Ligation 

 of the periarterial tissues in ten dogs, the artery itself being excluded from the 

 ligature, directly injured both muscular and nervous substance, but was only 

 once followed by arrest. Nor does arrest follow the ligation of a vein, although 

 the mechanical injury is possibly as great as in tying an artery. The direct 

 stimulation of the superficial ventricular nerves exposed to injury in the opera- 

 tion of ligation does not produce the effects that appear after the ligation of 

 coronary arteries. 



Against the remaining proposition stated above — namely, that anaemia with- 

 out mechanical injury does not cause arrest with fibrillary contractions — it 

 should be said that the frequency of arrest after ligation is in proportion to 

 the size of the artery ligated, and hence to the size of the area made anaemic, 

 and is not in proportion to the injury done in the preparation of the artery. 

 The circumflex and descendens may be prepared without injuring a single 

 muscle-fibre, yet their ligation frequently arrests the heart, while the ligation 

 of the arteria septi, which cannot be prepared without injuring the muscle- 

 substance, does not arrest the heart. It is, moreover, possible to close a coro- 

 nary artery without mechanical injury. Lycopodium spores mixed with de- 

 fibrinated blood are injected into the arch of the aorta during the momentary 

 closure of that vessel and are carried into the coronary arteries, the only way 

 left open for the blood. The lycopodium spores plug up the finer branches 

 of the coronary vessels. The coronary arteries are thus closed without the 

 operator having touched the heart. Prompt arrest with tumultuous fibrillary 

 contractions follows. There seems, then, to be no doubt that fibrillary contrac- 

 tions can be brought on bv sudden anaemia of the heart muscle. 1 



The gradual interruption of the circulation in the coronary vessels — by 

 bleeding from the carotid artery, for example — is followed by feeble inco- 

 ordinated contractions not essentially different in kind from those commonly 

 termed fibrillary contractions. The manner of interruption probably explains 

 the difference in result. In the former case, namely, ligation or other sudden 

 closure, the supply of blood to the heart muscle is suddenly slopped while the 

 heart continues to work against a high peripheral resistance ; in the latter, the 

 anaemia is gradual and the heart works against little or no peripheral resistance. 



Recovery from Fibrillary Contractions. — Fibrillary contract ions brought 

 on by clamping the left coronary artery in the rabbit's heart are often gradually 

 replaced by normal contractions when the clamp is removed. The isolated 

 cat's heart after showing marked fibrillary contractions during forty-five 

 minutes lias given strong regular beats for more than an hour. McWilliam 

 and others have seen a number of spontaneous regular beats after the termi- 

 nation of fibrillary contraction. The dog's heart can be recovered by cool- 

 ing the ventricles until all trace of fibrillation has disappeared, and then 

 bringing the hearf back to normal temperature by circulating warmed defi- 

 1 Porter: Journal oj Experimentul Medicine, 1896, I. p. 65. 



