COMPOSITION OF THE BLOOD. . 297 



6. Of tlie Composition and Properties of the Blood. 



524. Having traced the steps by which the Blood is elaborated, and 

 prepared for circulation through the body, and having (in the former 

 part of the volume) inquired into the characters of its chief consti- 

 tuents, we have now to consider the fluid as a whole, to study the usual 

 proportions of these constituents, and the properties which they impart 

 to it. 



525. The Blood, whilst circulating in the' living vessels, may be 

 seen to consist of a transparent, nearly colourless fluid, termed Liquor 

 Sanguinis; in which the Corpuscles, to which the blood owes its red 

 hue, as well as the white or colourless corpuscles, are freely suspended 

 and carried along by the current. On the other hand, when the blood 

 has been drawn from the body, and is allowed to remain at rest, a 

 spontaneous coagulation takes place, separating it into Clot and Serum. 

 The Clot is composed of a network of Fibrine, in the meshes of which 

 the Corpuscles, both red and colourless, are involved ; and the Serum 

 is the same with the liquor sanguinis deprived of its Fibrine. When 

 the Serum is heated, it coagulates, showing the presence of Albumen. 

 And if it be exposed to a high temperature, sufficient to decompose the 

 animal matter, a considerable amount of earthy and alkaline Salts 

 remains. Thus we have four principal components in the Blood: 

 namely, Fibrine, Albumen, Corpuscles, and Saline matter. In the 

 circulating Blood they are thus combined : 



Fibrine \ 



Albumen I In solution, forming Liquor Sanguinis. 



Salts J 



Red Corpuscles, Suspended in Liquor Sanguinis. 



But in coagulated blood they are thus combined : 



| Crassamentum or Clot. 

 | Remaining in solution, forming Serum. 



A certain amount of Serum, however, is involved in the Crassamentum ; 

 and can only be separated by 'cutting the clot into thin slices, and 

 carefully washing it. 



526. The components of the Blood may be separated, and their 

 amount estimated, in various ways. Thus, if fresh-drawn blood be 

 continually stirred with a stick, or be " whipped" with a bunch of 

 twigs, the Fibrine coagulates in the form of strings, which adhere to 

 the wood, and may thus be withdrawn ; whilst the red corpuscles then 

 remain suspended in the serum, gradually sinking to the bottom in 

 virtue of their greater specific gravity. On the other hand, the Red 

 Corpuscles may be separated, in those animals in which they are large 

 enough, by passing the blood through a filter ; having previously mingled 

 with it some substance which retards, but does not prevent its coagula- 

 tion* ( 185). The liquor sanguinis is thus separated from the blood- 



* This experiment cannot be performed with Human blood, because the corpuscles 

 are small enough to pass through the pores of any filter that allows the liquor sanguinis 

 to permeate it ; but it answers very well with Frog's blood. 



