DISJi^ASES OF THE CIRCULATORY SYSTEM. 237 



tonics had better be given some time after food — i. e., 

 not on an empty stomach. Pill f(.riii answers admirably. 

 Dogs often lick up cod-liver oil and phosphates (e. g., 

 Parrish's syrup) very well when stirred up in a little milk„ 



DISEASES OF THE BLOOD AND THE CIRCULATORY 



SYSTEM. 



The blood consists of an albuminous fluid in which 

 colored and colorless cells abound, the latter in relatively 

 scanty numbers. This fluid, owing to the arrangements 

 of the circulatory system, is conveyed to every part of 

 the body, but never during health actually escapes from 

 the containing vessels 



The principal function of the red cells is the convey- 

 ance of oxygen. The blood as a whole is at once the 

 source of supply for all tissues and the medium of re- 

 moval of all waste — i. e.^ all waste, gaseous and other, 

 sooner or later gets into the blood and is carried to those 

 various organs that serve to eliminate the diflersnt harm- 

 ful constituents. 



Nature, then, it would seem, is constantly striving to 

 maintain the equilibrium of the blood. When much is 

 taken from it the nervous system becomes conscious of it, 

 so to speak, and hunger for food or oxygen is the result ; 

 an attempt is made to furnish food and thus renew the 

 blood from the digestive supplies, while the lungs do the 

 work to furnish oxygen. It thus appears that there is a 

 very close relationship between the respiratory, circula- 

 latory, and digestive systems. (Fig. 14.) 



But in reality the tissues are not nourished directly by 

 blood, but by lymph, which may be regarded as an albu- 



