232 OF THE BLOOD: 



very far, so that it is not drawn from the venous system. A closer approxi- 

 mation may be made by opening several vessels at once, which was the 

 method adopted by Herbst ; l who estimated the proportion of the weight of 

 the blood to that of the entire bo.dy to be as 1 : 12 in the Ox, as 1 : 16 in the 

 Dog, as 1 : 18 in the Horse, as 1 : 20 in the Goat, Calf, Lamb, and Hare, as 

 1 : 22 in the Sheep and Cat, and as 1 : 24 in the Rabbit. With these esti- 

 mates the conclusions drawn by Vauuer, from observations made in the 

 abattoirs of Paris, pretty closely correspond ; for he was led by them to the 

 belief, that for horned cattle in general, the proportion does not vary far 

 from 1 : 20. 2 It is obvious, however, that no such method can give more 

 than a minimum; since, even after the most complete exsauguination that 

 the freest opening of the vessels can permit, a considerable quantity of blood 

 is still retained in them, and especially in those of the head. Various other 

 methods have been suggested, none of which, however, can be considered as 

 yielding more than approximations to the truth. That of Vierordt 3 consists 

 in multiplying the quantity of blood which is expelled from the left ventricle 

 at each pulsation of the heart by the number of beats which occur whilst the 

 blood performs one entire circuit of the body. He estimates the former 

 (highly) at 6.3 oz. av., and the latter at 27.7 beats ; consequently the total 

 quantity of blood is about 11 Ibs. av., or between one-twelfth and one-thir- 

 teenth of the weight of the body. Welcker's method, termed also the " chro- 

 matic" or "color" method, gives nearly the same result for Man and the 

 Dog. It consists in first roughly estimating the quantity of blood in the ani- 

 mal by rapidly bleeding it to death. The portion that still remains in the 

 small vessels is then removed by the injection of pure water, and the whole body 

 of the animal is finely minced and infused. These liquids are mingled, and 

 on comparing their tint with a series of previously prepared " color tests," 

 the proportion of blood in which is accurately known, a practiced eye may 

 discern variations in the color when the difference in the quantity of blood 

 does not exceed 4 per cent. Welcker estimates that a man weighing 143 

 Ibs. has 11 Ibs. of blood. An interesting collection of cases has been brought 

 together by Haller 4 of the amount of blood lost by haemorrhage ; and two 

 remarkable instances are cited by Burdach, 5 from Wrisberg, who states that 

 a female who died from violent rnetrorrhagia had lost 26 Ibs. of blood, and 

 that 24 Ibs. were collected from the body of a plethoric female who had suf- 

 fered death by decapitation. In the first of these cases, it is probable that, 

 as death could not have been immediate, some increase took place from the 

 absorption of the fluids of the body; in the second, however, the suddenness 

 of the discharge of blood, and its concurrence with the destruction of life, 

 must have prevented any considerable augmentation from this source ; and 

 if any such increase did take place, it probably did not exceed the amount 

 of blood remaining undischarged in the vessels. An important observation 

 has been made by Bernard, 6 that the quantity of blood which can be ob- 

 tained from a fasting animal is scarcely more than one-half of that contained 

 in its vessels shortly after a full meal : a point to which no other observer 

 appears to have paid attention, but which may account for some of the dis- 

 crepancies observable in the different estimates. 7 



1 DeSanguinis <|iiantilte, quails homini adulto et suno convenit. Goettingse, 18'J'J. 



2 Complex Kcndii.s, t>m. x.xviii, p. 64!>. 3 Phy>iologie, 18U4, p. 138. 

 4 Klementu I'hyMolMO-ia', vol. ii, pp. 3 and 4. 



6 Traite de Physiologie, trwhiit par Jourdain, torn, vi, p. 119. 



6 Lcrons, 1,-sY.t', t. i, p. 4 HI. 



7 Valentin's method is founded on the diminution in the specific gravity of the 



after the injection of a known weight of water into the vessels, and gave for 

 the proportion of the weight of blood to that of body generally as 1 : 4i (Report. 



