PHYSICAL AND VITAL PROPERTIES OF THE BLOOD. 527 



liquid which flows through the Thoracic duct into the venous system; and if 

 any inference can be fairly drawn from the measurement of the quantity de- 

 livered in the" course of a few minutes, it would appear that the total amount 

 thus transmitted in one day is nearly or quite equal to the entire mass of the 

 blood. At any rate, it so far exceeds the amount of liquid ingested, that we 

 must believe a large portion of it to be derived from the circulating current, 

 having been withdrawn from it for a time, to be again delivered into its stream, 

 after having undergone the requisite elaboration. 



5. Physical and Vital Properties of the Blood. 



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

 prepared for circulation through the body, and having formerly inquired into 

 the characters of its chief constituents (Chap. HI.), 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. The Blood, whilst circulating in the 

 living vessels, may be seen to consist of a transparent, nearly colourless, 

 liquid, termed Liquor Sanguinis; in which the Red Corpuscles, from which 

 the Blood of Vertebrated animals derives its peculiar hue, as well as the White 

 or Colourless corpuscles, are freely suspended and carried along by the cur- 

 rent. 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, sepa- 

 rating it into Crassamentum and Serum. The Crassamentum or Clot is 

 composed of a network of Fibrine, in the meshes of which the Corpuscles, 

 both red and colourless, are involved, together with a certain amount of serous 

 fluid. The Serum, which is the same with the Liquor Sanguinis deprived of 

 its Fibrine, coagulates by heat, and is therefore known to contain 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 com- 

 bined : 



Fibrine } 



Albumen > In solution, forming Liquor Sanguinis. 



Salts ) 



Corpuscles, suspended in Liquor Sanguinis. 



But in coagulated blood, they are combined as follows: 



i rinc i Crassamentum or Clot. 

 Corpuscles 3 



c > Remaining in solution, forming Serum. 



Ill the blood of Man and the higher Vertebrata, the Colourless Corpuscles 

 usually bear so small a proportion to the Red, that they have until recently 

 escaped notice. In Reptiles, however, they attract attention, from their 

 marked difference in size and form, even whilst the blood is moving through 

 the capillaries; and they are the more easily watched, owing to the compara- 

 tively small number of the Red Corpuscles in those animals. The blood of 

 the Invertebrata is usually pale, and contains very few red corpuscles ; indeed 

 they would seem to be absent altogether in the lower Articulata and Mollusca. 

 On the other hand, the colourless corpuscles are frequently very numerous, 

 especially during the periods of most active growth. The blood of these 

 animals may be likened, therefore, in many respects to the Lymph and Chyle 

 of the Vertebrata; and the resemblance is the more close, as there is no 



