THE BLOOD. 



235 



Color. When viewed by transmitted light, a single corpuscle is slightly 

 yellow or greenish in color; but when a number are grouped together, the 

 color deepens and the corpuscles appear red. In either case the color is due 

 to the presence in the corpuscle of a specific coloring-matter, hemoglobin. 



Shape. The red corpuscle is a 

 circular, flattened disk with rounded 

 edges. Each surface is perfectly 

 smooth and presents a shallow de- 

 pression in its center, so that it is 

 also biconcave. A longitudinal sec- 

 tion of a corpuscle would present, 

 when viewed edgewise, an outline 

 similar to that of Fig. 98. This 

 difference in the thickness of the 

 peripheral and central portions of 

 the corpuscle gives rise to differences 

 in optical appearances when ex- 

 amined microscopically. At a certain 

 distance of the object-glass the cor- 

 puscle presents in its peripheral por- 



FIG. 97. CORPUSCLES FROM HUMAN 

 SUBJECT. A few colorless corpuscles are 

 seen among the colored discs, many of 

 which are arranged in rouleaux. (Funke.) 



FIG. 98. IDEAL TRANSVERSE 

 SECTION OF A HUMAN RED CORPUS- 

 CLE. (Magnified 5000 times.) a, b. 

 Diameter, c, d. Thickness. - 



tion a bright rim, and in its central 

 portion a dark spot If the objective 

 be brought nearer and the center 

 accurately focused, the reverse ap- 

 pearance obtains; the central portion becomes bright and the peripheral 

 portion dark. The cause of this difference in optical appearance is the 

 unequal distribution of the transmitted light in consequence of the shape 



c of the corpuscle. 



Size. The diameter of a typical well- 

 developed red corpuscle under normal con- 

 ditions is 0.0075 mm., its greatest thick- 

 ness is 0.0019 mm. Though this may be 

 assumed as the average diameter, there 

 is a small percentage of distinctly smaller 

 and a small percentage of distinctly larger 

 corpuscles. The following table shows the results of measurement made 

 by different observers: 



Normal Limits. Average Diameter. 



Welcker diameter o .0045-0 .0095 mm o .0070 mm. 



Hayem ; . . . .diameter 0.0060-0.0088 mm 0.0075 mm. 



Gram diameter 0.0067-0.0093 mm 0.0078 mm. 



Melassez o .0076 mm. 



0.00747 (goVo inch) 



Structure. The red corpuscle of man as well as of all other mammals 

 possesses neither a nucleus nor a limiting membrane, but appears to consist 

 of a homogeneous substance more or less semisolid in consistence. Under 

 the influence of certain reagents the corpuscle separates into two distinct 

 portions: viz., a colorless protoplasmic stroma and a coloring-matter which 

 diffuses into the surrounding liquid. The presence of the former can be 

 demonstrated by the addition of iodin, which imparts to it a faint yellow color. 



