220 



THE BLOOD. 



rjj.pti.les, and fish, the blood-globules differ so much from the above 

 that they can be readily distinguished by microscopic examination. 

 They are oval in form, and contain a colorless granular nucleus 

 imbedded in their substance. They are also considerably larger 

 than the blood-globules of the mammalians, particularly in the 



class of reptiles. In the frog 



Fig. 60. (Fig. 60) they measure T ^ T 



of an inch in their long 

 diameter ; and in Menobran- 

 chus, the great water lizard 

 of the northern lakes, 7 ^^ of 

 an inch. In Proteus angui- 

 nus they attain the size, ac- 

 cording to Dr. Carpenter, 1 of 

 5^7 of an inch. 



Beside the corpuscles de- 

 scribed above, there are glo- 

 bules of another kind found 

 in the blood, viz., the white 

 globules. These globules are 

 very much less numerous 

 than the red; the proportion 



between the two, in human blood, being one white to two or three 

 hundred red globules. In reptiles, the relative quantity of the 

 white globules is greater, but they are always considerably less 

 abundant than the red. They differ also from the latter in shape, 

 size, color, and consistency. They are globular in form, white or 

 colorless, and instead of being homogeneous like the others, their 

 substance is filled everywhere with minute dark molecules, which 

 give them a finely granular appearance. (Fig. 54, c.) In size they 

 are considerably larger than the red globules, being about 25 V<r of 

 an inch in diameter. They are also more consistent than the others, 

 and do not so easily glide along in the minute currents of a drop of 

 blood under examination, but adhere readily to the surfaces of the 

 glass. If treated with dilute acetic acid, they swell up and become 

 smooth and circular in outline ; and at the same time a separation 

 or partial coagulation seems to take place in the substance of which 

 they are composed, so that an irregular collection of granular 

 matter shows itself in their interior, becoming more divided and 



BLOOD-GLOBUL KS OF FROG. 

 seen edgewise, b. White-globule. 



a. Blood-globule 



The Microscope and its Revelations, Philadelphia edition, p. 600. 



