Tilt BLOOD OF ANIMALS. 



101 



variations, increasing rapidly after a meal, and falling as 

 rapidly. 



There is less blood in cold-blooded than in warm-blood- 

 ed animals ; and the larger the animal, the greater is the 

 o 





Fig. <>6.— Capillary Circulation iu the Web.of a Fj'ng's Foot, X 100: a, b, small veins', 

 d, capillaries in which the rtval corpiisCl^s^are seen to follow one another in sin* 

 gle series ; c, pigment-cells in the skin. 



proportion of blood to the body. Man has about a gallon 

 and a half, equal to one thirteenth of his weiglit. The 

 heai-t of the Greenland Whale is a yard in diameter. 



Tlie main Office of t-he Blood is to supply nourish- 

 ment to, and take away waste matters from, all parts of 

 tlie body. It is at once purveyor and scavenger. In its 

 circulation, it passes, while in the capillaries, within an in- 

 tinitesimal distance of the various tissues. Some of the 

 plasma, carrj-ing the nutritive matter needed, exudes 

 through the walls of tlie capillar}' tubes; the tissue assimi- 

 lates or makes like to itself whatever is suitable for its 

 growth and repair; and tlie lympliatics take up the tran- 



