31 GENERAL ANATOMY. 



white (Harley); by others only fifty times as numerous (Todd and Bowman). 1 

 They differ very much in size and shape in different animals (Fig. 1). In man 

 their size varies considerably, even in the same drop of blood, between the 

 limits of 5^53 and jjg 1 ^ of an inch in diameter, the average being about 



Fijr. 2. 



Corpuscles of Frog's blood : 1, 1, red corpuscles seen on Human blood-globules : a, seen from the 



their flattened face ; 2, the same turned nearly edgeways ; surface; b, from the side; c, united in rou- 

 3, colorless corpuscles ; 4, red corpuscles altered by dilute leaux ; d, rendered sphericnl by water ; e, de- 

 acetio acid.] colorized by the same ; f t blood-globules 



shrunk by evaporation. 



(Todd and Bowman). They are circular disks, bi-concave in profile, having a 

 slight central depression, with a raised border (as seen in Fig. 2, b). Their 

 color appears of a faint yellow when they are seen singly, but it is to their 

 aggregation that the blood owes its red hue. Human blood-disks present no 

 trace. of a nucleus. When the blood is circulating, under the microscope, in 

 one of the lower animals, the blood-globules are seen to be separate from each 

 other, and are also separated from the wall of the vessel by an interval or 

 " lumen." Doubtless the same is the case in the human body ; but when 

 drawn and examined on a slide without reagents, the blood-globules often 

 collect into heaps like rouleaux of coin (Fig. 2, c). Their shape is very soon 

 influenced by the medium in which they are placed, and by the specific gravity 

 of that medium. In water they swell up, lose their color, and cease to be 

 visible, leaving the white corpuscles in the field. Solutions of salt or sugar, 

 denser than the serum, give them a stellate appearance; and the usual shape 

 may be restored by diluting the solution to the proper point. A solution of 

 the proper strength merely separates the blood-globules mechanically, without 

 changing their shape. 



There can be no doubt that the difference in color between arterial and 

 venous blood must be due to some minute difference in the red blood-globules; 

 and it is also in the highest degree probable that the chemical differences 

 between these two kinds of blood are due, in part at least, to such differences; 

 but the change has not hitherto been rendered perceptible either to the micro- 

 scope or to chemical analysis. At the same time, the researches of Professor 

 Stokes 2 show that the coloring matter of the blood produces different effects 

 on the solar spectrum, according as it is in a more or less oxidized condition; 

 and it is in the highest degree probable that the same change in the oxidation 

 of the contents of the blood-globules produces the difference of color between 

 arterial and venous blood. 



The human white corpuscles are rather larger than the red, and have an 

 irregular or granular surface. A nucleus becomes perceptible on the addition 

 of acetic acid. They are very similar, if not identical, with the corpuscles of 

 the lymph and chyle, though somewhat more acted upon by acetic acid than 



1 Hirt puts the proportion as low as 1 : 1761 during fasting, and 1 : 695 or 1 : 429 after food 

 (Kolliker). Venesection, by -withdrawing so much larger a proportion of the red globules, and 

 also by favoring the absorption of lymphatic fluid into the blood, much increases the relative 

 proportion of the white corpuscles, so that Kolliker asserts that in the horse, after enormous 

 venesection (up to 501bs.) the colored and colorless corpuscles appear equally numerous. 



2 Proceedings of Royal Society, 1864. 



