THE BLOOD. 475 



through which it is propelled by an active heart. If derived 

 from the arterial system, it is found of a bright scarlet hue, 

 and if from the veins, it is of a dark Modena red colour. 

 Bernard has shown that the venous blood flowing from some 

 glands is bright red, owing probably to its purification by the 

 excreting process within the gland. Blood has a saltish taste, 

 a smell characteristic of the animal from which it is derived, 

 and by which Barruell thought he could detect at any time 

 from what animal blood might have been obtained. Blood 

 has a specific gravity, varying from 1.052 to 1.057, and it is 

 found composed of various materials, which are obtained sepa- 

 rate under different circumstances. Within the body, blood is 

 seen to be composed of blood-particles flowing in a blood 

 liquid, or liquor sanguinis; outside the body, it clots and 

 separates into clot and serum. The following table shows 

 the change occurring from fluid to coagulated blood : 



Circulating blood. 



Blood particles. Liquor sanguinis. 



Fibrin. Serum. 



Clot. 



Coagulated blood. 



Blood is warm; its temperature amounts to about 100 

 Fahr., it varies from 98 to 100 in health, ascending in fever 

 as high as 107, and occasionally being as low as 96 as in 

 cyanosis. 



If a drop of blood is placed under the microscope, with a 

 little pure serum or water, blood particles are found dispersed 

 in the field in large numbers. A multitude of red flattened 

 discs, with a depression on either side, are seen free or running 



