AMOUNT OF BLOOD. 211 



thin layer on a piece of glass over the page of a book. This 

 opacity depends on the fact that the blood, as will presently be 

 seen, is not a red fluid, but owes its color to the presence of solid 

 red particles or corpuscles which float in a clear pale fluid. The 

 blood has a peculiar smell (halitus) distinct in different animals 

 and man, dependent on certain volatile fatty acids. Its specific 

 gravity varies from 1045 to 1075, the average being 1055. The 

 solid parts (corpuscles) are heavier (sp. gr. 1105) than the liquor 

 sanguinis-(1027). 



When first shed the blood has a slippery feel, which it soon 

 loses, becoming sticky as it passes through the various stages of 

 the process of coagulation. 



AMOUNT OF BLOOD IN THE BODY. 



The total amount of blood has been estimated to be from ^ to y^ 

 of the body-weight for an adult man, and somewhat less for a new- 

 born child. 



Much difficulty has been found in arriving at an accurate esti- 

 mation of the amount of blood in the body. In the first place, all 

 the blood cannot be made to flow out of the vessels of an animal 

 when it is killed. Secondly, the quantity and quality of blood 

 are constantly varying with the capacity of the bloodvessels. 

 Thirdly, when slowly withdrawn from the body during life it is 

 rapidly replaced by more fluid passing into the bloodvessels. 

 This explains the enormous quantity of blood occasionally reported 

 to be shed in cases of bleeding to death. In these cases, as quickly 

 as the blood is lost, fluid is absorbed by the fine vessels to replace 

 it, so that if the bleeding be gradual the standard quantity is still 

 kept up in the vessels. Thus the very sudden loss of a compara- 

 tively small quantity of blood may cause death, whereas, if the 

 bleeding go on sufficiently slowly and gradually, as much or even 

 more in quantity than normally exists in the entire body may es- 

 cape without fatal result, but of course much of this is fluid which 

 has recently entered the vessels to replace the blood already lost. 



Weber's Method. The percentage of solid matters in the blood 

 is first carefully estimated. The absolute quantity of solids in 

 the drawn blood is then ascertained and added to the solids ob- 





