BOOK V. 



ClECULATOEY APPARATUS, 



The animal economy is incessantly traversed by two fluids — blood and 

 lymph. 



The blood is a liquid, coloured bright-red or brown by particular globules, 

 from which the tissues derive not only the materials for nutrition and 

 secretion, but also the exciting principle which vivifies the organic 

 matter. It is named red or dark-coloured blood, according to its 

 tint. 



The lymph or white blood is a transparent, citrine-coloured fluid, which 

 can be obtained from the majority of the organs. That which comes from 

 the abdominal portion of the alimentary canal is charged, during digestion, 

 with a portion of the reparative materials elaborated in that apparatus, and 

 is distinguished by its lactescent aspect ; it is designated the chyle. 



Fig. 257. 



THEORETICAL PLAN OP THE CIHCDLATORT SYSTEM. 

 (h, d, c, e, The canal for red blood ; E, B, A, S, Canal for black blood. The arrows 

 indicate the course of the blood. The two canals are represented in their middle 

 portion, ab, cd, as isolated ; but in nature they are enveloped at this point in a 

 common sac that concurs to form the heart.) 



These fluids are carried by vessels — tubes which are continuous with one 

 another. When joined together, end to end, these tubes give rise to three 

 principal canals : 



"One of these canals extends from the lungs to all parts of the body, 

 and IS traversed by red blood. 



