296 



THE HUMAN BODY 



Sometimes the corpuscle (Fig. 97, B) appears circular; then it is 

 seen in full face; sometimes linear (C), and slightly narrowed in 

 the middle; sometimes oval, as the dollar when halfway between 

 a full and a side view. These appearances show that each red 

 corpuscle is a circular disk, slightly hollowed in the middle (or 

 biconcave) and about four times as wide as it is thick. The av- 

 erage transverse diameter is 0.008 millimeter (swff inch). Shortly 

 after blood is drawn the corpuscles tend to arrange themselves in 

 rows, or rouleaux, adhering to one another by their broader sur- 

 faces. 



Color. Seen singly each red corpuscle is of a pale yellow color; 

 it is only when collected in masses that they appear red. The 



FIG. 97. Blood-corpuscles. A, magnified about 400 diameters. The red corpus- 

 cles have arranged themselves in rouleaux; a, a, colorless corpuscles; B, red cor- 

 puscles more magnified and seen in focus; E, a red corpuscle slightly out of focus. 

 Near the right-hand top corner is a red corpuscle seen in three-quarter face, and at 

 C one is seen edgewise. F, G, H, I, white corpuscles highly magnified. 



blood owes its red color to the great numbers of these bodies in it; 

 if it is spread out in a very thin layer it, too, is yellow. 



Structure. There is no satisfactory evidence that these cor- 

 puscles have any enveloping sac or cell-wall. All the methods 

 used to bring one into view under the microscope are such as 

 would coagulate the outer layers of the substance composing the 

 corpuscle and so make an artificial envelope. So far as optical 



