CHAPTER III. 



BLOOD SYSTEM. 



Returning again to man, we have now carried the 

 food to the blood. We therefore take next the blood 

 system. But first of all we must say something about 

 the blood itself. 



SECTION I. 

 The Blood. 



Blood is an intensely red fluid, of a slightly viscid 

 feel and a faintly nauseous smell and taste. To the 

 naked eye it is quite homogeneous, but under the micro- 

 scope it is easily seen to consist of a multitude of solid 

 red particles or globules floating in an almost colorless 

 liquid. The liquid part is called plasma. The color is 

 wholly due to the globules. The quantity of this fluid 

 in a healthy man is about one and a half gallon. 



i. The Globules. — These are of two, possibly three 

 kinds, viz. : (a) the red globules (Fig. 235) ; (U) the white 

 or colorless globules ; and, doubtfully, (c) the blood plates. 

 Of these the red are far the most numerous and conspic- 

 uous, and are therefore taken first. 



(a) Red Globules. — These in size are about -3^5- inch 

 ( 1 | g millimetre) in diameter. In shape they are flattened 

 circular disks, a little depressed in the middle, their 

 thickness being about one quarter the diameter of the 

 disk. Their immense number may be shown thus : 

 From the size given above it is evident that it would 



347 



