318 OF THE CIRCULATION OF THE BLOOD. 



found to be entirely obliterated. 1 The total quantity discharged from either 

 ventricle of the Human heart at each systole is estimated by Valentin at 

 5.3 oz., by Volkraann at 6.2 oz., and by Vierordt at 6.3 oz. ; but these 

 amounts are deduced from calculation of the (supposed) total of the blood, 

 divided by the estimated duration of its passage through the heart, rather 

 than from actual admeasurement. The time occupied by the Blood in mak- 

 ing an entire circuit of the body was attempted to be ascertained by Hering, 2 

 by introducing prussiate of potass into one part of the system, and drawing 

 blood from another. He states that he detected this salt in blood drawn 

 from one of the jugular veins of the Horse in about 30 seconds after it had 

 been introduced into the other; in which brief space the blood must have 

 been received by the heart, have been transmitted through the lungs, have 

 returned to the heart again, have been sent through the carotid artery, and 

 have traversed its capillaries. These experiments have been fully confirmed 

 by those of Poiseuille,* and of Mr. Blake, 4 who found that a solution of 

 nitrate of baryta injected into the jugular vein of a horse appeared in the 

 blood of the carotid artery of the opposite side after an interval of 15 sec- 

 onds. The same inquiry has been pursued, with improved means, by Vie- 

 rordt. 5 This observer affixed a number of small cups to a drum which was 

 made to rotate at a certain velocity in front of the opened vein ; analyses 

 of the contents of the several vessels enabled him to ascertain with great 

 accuracy the moment at which the salt injected made its appearance. In 

 this way he determined the number of seconds occupied by the blood in per- 

 forming one entire revolution to be, in Squirrels 4.39, in Cats 6.69, in the 

 Hedgehog 7.61, in Rabbits 7.79, in the Dog 16.7, in the Horse 31.5, in the 

 Cock 5.17, in the Duck 10.64, and in the Goose 10.86. -He estimates the 

 period in Man at 23.1 seconds (during which there are 28 beats of the heart), 

 of which 2 seconds at most are occupied in traversing the larger arteries, 2|- 

 to 3 seconds in passing through the smaller arteries, 3 seconds for the cap- 

 illaries, and 4 or 5 seconds for the venous system, which numbers must be 

 multiplied by two for the two circulations. Moreover, the coincidence be- 

 tween the cessation of the heart's action and the diffusion of the salt through 

 the arterial blood bears a striking correspondence; and it may be hence 

 inferred that the arrestment of its muscular movement is due to the effect 

 of this agent upon its tissue, when immediately operating upon it, through 

 the capillaries of the coronary artery. This conclusion is borne out by a 

 variety of other experiments; which show that the time of the agency of 

 other poisons that suddenly check the heart's action (which is the special 

 property of mineral poisons), nearly coincides, in different animals, with that 

 which is required to convey them into the arterial capillaries. And it seems 

 to derive full confirmation from the fact, that poisons which act locally on 

 other parts give the first indications of their operation in the same period 

 after they have been introduced into the venous circulation. Thus, in the 

 Horse, the time that is required for the blood to pass from the jugular vein 

 into the capillary terminations of the coronary arteries is 16 seconds, as is 

 shown by the power of nitrate of potass to arrest the heart's action within 

 that time ; and nitrate of strychnia injected into a vein gave the first mani- 

 festation of its action on the Spinal Cord in precisely the same number of 

 seconds. In the Dog, the heart's action was arrested by the nitrate of potass 

 in 11 or 12 seconds; and the tetanic convulsions occasioned by strychnia 



1 Kirkos and Ptiget's Handbook of Physiology, 2d edit , p. 80. 



' Tii'dtMiiaim's /rksclirift, vol. iii, p. 85. 



:t Annul, dos Si-icnccs Nat., 184:!, Xool., t. xix, p. 32. 



4 Edin. Med. and Surg. Journ., Oct. 1841. 5 Phys. d. Mensch., 18G1, p. 111. 



