184 



AN AMERICAN TEXT-BOOK OE PHYSIOLOGY. 



brinated blood through the coronary vessels. 1 Recovery has also been obtained 

 by passing immediately (within 15 seconds) a very rapid alternating current 

 of not too great intensity. 2 



Closure of the Coronary Veins. — Closure of all the coronary veins in 

 the rabbit produced fibrillary contractions alter from fifteen to twenty minutes 

 had passed. Their closure in the dog is said to be without effect 3 — a negative 

 result perhaps to be explained by the fact that a portion of the coronary blood 

 finds its way to the cavities of the heart through the venae Thebesii. 



Volume of Coronary Circulation. — Bohr and Henriques, 4 taking the 

 average of six experiments on dogs, found that 16 cubic centimeters of blood 

 passed through the coronary arteries per minute for each 100 grams of heart 

 muscle. The quantity passing through both coronary arteries varied in dif- 

 ferent animals from 20 to 64 cubic centimeters per minute; the quantity 

 passing through the left coronary artery varied from 22.5 to 60 cubic centi- 



mm 



^^mmmmmm^M-u^ 



U-44-f4WirWW^ 



Fig. 40.— Diminution of the force of contraction of the ventricle of the Isolated cat's heart in con- 

 sequence of diminishing the supply of blood to the cardiac muscle : A, blood-pressure at the root of the 

 aorta, recorded bya mercury manometer; B, intra-ventrieular pressure-curve, left ventricle: the indi- 

 vidual beats do not appear, l ause of the slow >i d of the smoked surface; C, time in seconds; D, the 



number of drops of blood passing through the coronary arteries, each vertical mark recording one drop. 

 As the number of drops of blood passing through the coronary arteries diminishes, the contractions of 

 the hit ventricle become weaker, but ret-over again when the former volume of the coronary circula- 

 tion Is restored. 



meters per minute. The hearts weighed from 51 to 350 grams. The method 

 which Bohr and Henriques found it necessary to employ placed the hear! 

 under such abnormal conditions that their results can be regarded as only 

 approximate. Porter 8 supplied the left coronary artery of the dog with blood 

 diluted one-half with sodium chloride solution (0.6 per cent.) by means of a 

 tube ( lumen 2.75 millimeters I inserted into the aortic opening of the left coro- 



1 Porter: American Journal of Physiology, L898, i. p. 71. 



2 Prevost and Battelli : Journal de physiologie it de paihologie generate, 1900, p. 440. 

 'Michaelis: Zeitsehrift fur klinische Median, L894, xxiv. |>. 291. 



* Bohr and Henriques: Skandinavisches Archivfur Physiologie, 1895, v. p. 232. 

 iter: Journal of Experimental Medicine, 1896, i. p. 64. 



