THE CORONARY CIRCULATION. 165 



In 1698, Chirac 1 tied one of the coronary arteries in the dog, and 

 found that the heart soon ceased to beat. Jenner established a patho- 

 logical connection between angina pectoris and the reduction of the 

 coronary circulation attending calcification of these arteries. 



" The death of John Hunter in a paroxysm of angina, and the 

 discovery that his coronary arteries were indeed calcareous, as Jenner 

 had predicted, was a great stimulus to the clinical and pathological 

 study of these vessels." Erichsen 2 tied the coronary arteries in the 

 dog, and found the ventricles ceased to beat in a few minutes. The 

 musculature of the ventricles speedily passes into inco-ordinate fibrillar 

 contractions (delirium cordis). Ligaturing one of the large branches 

 only is frequently sufficient to cause arrest, 3 especially when the 

 heart is lowered in vigour by cooling and exposure, or when the 

 circulation is feeble. Arrest is produced in over 60 per cent, of the 

 cases when the ramus circumflexus is ligatured alone. Ligature of either 

 the right coronary artery or the ramus descendens far less frequently 

 produces a fatal result. As the heart begins to fail after the ligation 

 has been effected, the intraventricular and the aortic pressures 

 steadily fall, while the diastolic pressure in the left ventricle and 

 auricle rises, the ventricular beat becomes irregular, and the systolic 

 output greatly lessened. 



The heart after arrest, and even after it has passed into delirium 

 cordis, can often be revived by re-establishing the coronary circulation. 

 The failure of the heart is due to the anaemia produced. 4 This is so, 

 because (1) the severity of effect depends on the size of the artery ; 

 (2) the arrest can be produced by the injection of lycopodium spores 5 

 into the coronary circulation, and without any mechanical interfer- 

 ence with the heart ; (3) the arteries may be exposed and prepared 

 for ligation, and no arrest follows until the ligatures are drawn tight. 6 



Closure of all the coronary veins produces fibrillar contraction of 

 the heart in the rabbit. This does not occur in the dog, owing to 

 the fact that the blood can still find an exit into the cavities of the 

 heart through the venae Thebesii. 



On establishing an artificial circulation through the left coronary 

 artery of the isolated heart of a cat, Porter 7 found that strong and 

 regular contractions were maintained by a circulation of 4 cm. of blood 

 per minute. Probably about 10 to 20 cms. of blood per minute must 

 pass through the coronary circulation to maintain the heart of a 

 moderate-sized dog in efficiency. While the force of the ventricular 

 contraction is immediately increased by a greater flow of blood through 

 the coronary arteries, the frequency of the heart is largely independent 

 of the blood supply. 8 



1 "Demotu Cordis, " Monspelii. 1698, p. 121. 



2 Land. Hosp. Gaz., 1842, vol. ii. 561-564. 



3 Cohnheim and Bechberg, Virch&w's Archiv, 1881, Bd. Ixxxv. S. 503 ; Mac William, 

 Journ. PhysioL, Cambridge and London, 1887, vol. viii. p. 296 ; Bethelheim, 

 Ztschr. f. klin. Med., Berlin, 1892, Bd. xx. S. 436; Porter, Arch. f. d. ges. 

 PhysioL, Bonn, 1894, Bd. Iv. S. 336; Journ. PhysioL, Cambridge and London, 1894, 

 vol. xv. p. 121. 



4 Fenoglio and Drogoul, Arch. ital. de biol., Turin, vol. ix. p. 49. 



5 See, Bochefontaine, and Roussy, Compt. rend. Acad. d. sc., Paris, 1881, p. 86. 



6 Porter, CentralU. f. PhysioL, Leipzig u. Wien, 1896, S. 57. 



7 Porter, loc. cit. ; cf. Bohr and Henriques, Bull. Acad. d. sc. de Danemark, 1893 ; 

 Magrath and Kennedy, Journ. Exper. Med., New York, 1897, p. 13. 



8 Magrath and Kennedy, loc. cit. 



