GENERAL CONSIDERATIONS. 155 



be taken as a measure ; since, however freely it may be permitted to escape, a 

 considerable quantity still remains within the bloodvessels, especially if the 

 heart's action fail before the loss of blood has proceeded very far, so that it 

 is not drawn from the venous system. A closer approximation may be made 

 by opening several vessels at once, which was the method adopted by Herbst j 1 

 who estimated the proportion of the weight of the blood to that of the entire 

 body 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 estimates, the conclusions drawn by Vanner, 

 from his recent observations in the abattoirs of Paris, pretty closely correspond ; 

 for he is led by them to the belief, that for horned cattle in general, the propor- 

 tion 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 exsanguina- 

 tion 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. And 

 there are various observations which lead to the belief, that such estimates are 

 far too low as regards Man ; since it appears that a quantity of blood equal to at 

 least one-tenth of the weight of his body may be poured forth from his vessels 

 within a short time. Still, occurrences of this kind, of which Haller has brought 

 together an interesting collection, 3 afford but an unsafe basis for our estimate ; 

 since it is necessary to allow for the fact, that when the vessels are becoming 

 emptied of blood, a transudation of fluid takes place into them from the surround- 

 ing tissues, as is evidenced by the diminution in the specific gravity, and in the 

 increase in the proportion of water, which are apparent when even the first and 

 last parts of the blood drawn at an ordinary venesection are compared ( 162) : 

 so that, if the hemorrhage be going on for some hours, a much larger quantity 

 of fluid may be poured forth from the vessels than was ever contained within 

 them at any one time; and if liquids be ingested during its continuance, a por- 

 tion of these, being at once received into the circulating current, will go to aug- 

 ment the amount which escapes from it. Two remarkable instances of this kind 

 are cited by Burdach 4 from Wrisberg, who states that a female who died from 

 violent rnetrorrhagia lost 26 Ibs. of blood, and that 24 Ibs. were collected from 

 the body of a plethoric female who had suffered death by decapitation. In 

 the first of these cases, it is probable that, as death could not have been imme- 

 diate, some increase took place from 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. Another mode of 

 determining the total amount of the circulating blood has been proposed by 

 Prof. Valentin; 5 who first draws a sample of blood from an animal, and ascer- 

 tains the proportion of water which it contains, then injects a determinate quantity 

 of water into the vessels, and immediately draws fresh samples from different 

 parts of the body, in which also he ascertains the proportion of the solid to the 

 fluid components ; and from the amount of dilution which the last-drawn blood 

 exhibits, as compared with the first sample, he calculates the whole bulk of the 

 circulating fluid. From these data, Prof. Valentin estimated the proportion of 

 blood in the Dog as 1 : 4?, and in the Sheep as 1 : 5; so that, applying the former 

 of these proportions to the Human body, a man weighing 145 Ibs. would have 



1 "De Sanguinis quantitate, qualis komini adulto et sano convenit." Goettingee, 1822. 



2 "Comptes Rendus," torn, xxviii. p. 649. 



8 " Elementa Physiologies," vol. ii. pp. 3, 4. 



4 " Traite de Physiologic," traduit par Jourdain, torn. vi. p. 119. 



6 "Repert. fur Anat. und Phys.," band iii. p. 281. 



