336 STRUCTURE OF THE SHEEP. 



with heat ; and although it is the source whence other fluids 

 are obtained, it is yet a fluid sui generis, differing from all 

 others. Soon after it is drawn from the body it coagulates, 

 and then separates into two parts : the serum, a watery, col- 

 orless fluid, which floats on the top, and the crassamentum, 

 which appears of a firm consistency and a red color. The 

 serum is a peculiar fluid, and may be separated into its con- 

 stituent principles. If subjected to a temperature of 150®, 

 a portion is converted into a substance resembling albumen 

 or the white of an egg ; the other portion remains fluid and 

 is termed the serosity of the blood, and is that which consti- 

 tutes the gravy in meat. The serum contains several salts 

 in solution, the most abundant of which is soda. The 

 crassamentum is likewise divisible into two portions : the 

 cruor, w hich gives to the blood its purple hue ; and the 

 lymph, which is more solid in its nature, and is considered 

 the basis of the coagulum. The latter can be separated from 

 the former by washing, and likewise separates when the 

 blood is a long time coagulating, in which case the red por- 

 tion of the blood, being the heaviest, falls to the bottom of 

 the vessel, leaving the lymph on the top. The cruor, or 

 red portion of the blood, has been found, on being submitted 

 to a microscope, to be composed of globules, which are sup- 

 posed to be each about the three or four thousandth 

 part of an inch in diameter. It is therefere to these glo- 

 bules that the blood owes its redness ; but the intensity of 

 the color is subject to great variation, being darker in animals 

 that are poorly fed, or when exposed to carbonic acid, and 

 becoming more florid in others that are well fed, and also 

 when exposed to oxygen, or to atmospheric air. 



The other part of the crassamentum, the lymph, which from 

 its nature is also called the fihrine, is, in fact, the most im- 

 portant of all ; for it is that which mainly supplies the dif- 

 ferent parts of the body, particularly the muscles, with nu- 

 triment, and repairs wounds and fractures in an extraordinary 

 manner. Unlike the cruor, it exists in the blood of all ani- 

 mals, and in every part of the system. Some animals have 

 entirely white blood, the cruor being absent ; and in red- 

 blooded animals there are some portions of the body, such 

 as the white of the eye, where the vessels are so small that 

 they do not admit the red globules. The specific gravity of 

 blood rather exceeds that of water ; but venous blood is 

 somewhat heavier than arterial. The temperature of the 



