22 



AMOUNT OF BLOOD EXISTING IN ANIMALS. 



are provided with such an enormous external skeleton, that the errors in the calcu- 

 lation of the amount of iron in this would be numerous. 



The only practical method which I was able to devise, was, to cut the j-ugular 

 veins and arteries, and, stretching the neck out, hold the body perpendicular, with 

 the head downwards. The contraction of the heart, bloodvessels, and capillaries, 

 aided by gravity, expelled very nearly all the blood; a fact which was often 

 proved by the thin, watery aspect of the last portions. 



This method is more accurate in cold than warm-blooded animals, because their 

 nervous and muscular system, requiring but little nutriment from the blood, the 

 heart continues to beat, and the muscles, bloodvessels, and capillaries to contract, 

 for hours after almost all the blood has been abstracted. In warm-blooded animals, 

 the heart ceases to beat, and the contractility of the muscular system is lost, when 

 not more than one-third of the blood has been abstracted. This method, then, 

 which I employed to determine the amount of blood in cold-blooded animals, should 

 not be condemned because it is not applicable to warm-blooded animals. 



Great discrepancies have prevailed amongst physiologists witli regard to the 

 amount of blood contained in the bodies of warm-blooded animals. 



Blumenbach estimated the quantity in an adult man at 8.5 to 11 pounds, and 

 Eeil at 44 pounds. 



M. Valentin, by his method of injecting water, arrived at the following results. 

 The numbers represent the relation existing between the quantity of blood and 

 the weight of the body. 



Large Dogs (the mean of four experiments) . . . . as I : 4.5 



A lean, debilitated Sheep . . . . . . as 1 : 5.02 



Cats, female (the mean of two experiments) . . . . as 1 : 5.78 



A large female Uabbit . , . . . . as 1 : 6.20 



From these data, he estimated the amount of human blood to be 



Male sex . . . . . . . - . as 1 : 4.36 



Female sex . . . . . . . . as 1 : 4.93 



At the present day, the blood is generally estimated at 22 pounds, which is equal 

 to about the eighth part of the weight of the body. 



Lehmann^ determined the amount of blood in the bodies of two criminals, who 

 Avere decapitated, to be from 17.5 to nearly 19 pounds, or one-eighth the weight of 

 their bodies. 



From numerous careful examinations of cold-blooded animals, by the method 

 previously described, I have arrived at the following results, which must be con- 

 sidered only as an approximation to the truth. 



Amount of blood in Serpents . ' . . j\ to j\ of the weight of body. 



" Emys terrapin . . -Jy to y'y " " 



" Emys serrata . . to j'y " " 



" Tcstudo ■pohjphemus . . j\ to " " 



^ Loc. cit., p. 638. 



