THE BLOOD 



75 



of the whole mass of the blood. The proportion of colorless corpuscles 

 is only as 1 to 500 or 600 of the colored. 



Red or Colored Corpuscles. Human red blood-corpuscles are 

 circular, biconcave disks with rounded edges, from -3-^-5- to o Vo i ncn i* 1 

 dia-metiT, and y^-o^- inch in thickness, becoming flat or convex on addi- 

 tion of water. When viewed singly, they appear of a pale yellowish tinge; 

 the deep red color which they give to the blood being observable in them 

 only when they are seen en masse. They are composed of a colorless, 

 structureless, and transparent filmy framework or stroma, infiltrated in 

 ill parts by a red coloring matter termed hemoglobin. The stroma is 

 tough and elastic, so that, as the cells circulate, they admit of elongation 

 and other changes of form, in adaptation to the vessels, yet recover their 

 natural shape as soon as they escape from compression. The term cell, 

 in the sense of a bag or sac, is inapplicable to the red blood corpus- 

 cle; and it must be considered, if not 

 solid throughout, yet as having no such 

 variety of consistence in different parts 

 as to justify the notion of its being a 

 membranous sac with fluid contents. 

 The stroma exists in all parts of its sub- 

 stance, and the coloring-matter uni- 

 formly pervades this, and is not merely 

 surrounded by and mechanically en- 

 closed within the outer wall of the 

 corpuscle. The red corpuscles have 

 no nuclei, although, in their usual state, 

 the unequal refraction of transmitted FIG es.-Red corpuscles in rouleaux At 

 light gives the appearance of a central ,^ are two white corpuscles. 



>t, brighter or darker than the border, according as it is viewed in or 

 mt of focus. Their specific gravity is about 1088. 



Varieties. The red corpuscles are not all alike, some being rather 

 larger, paler, and less regular than the majority, and sometimes flat or 

 slightly convex, with a shining particle apparent like a nucleolus. In 

 almost every specimen of blood may be also observed a certain number of 

 corpuscles smaller than the rest. They are termed m.icrocytes, and are 

 probably immature corpuscles. 



A peculiar property of the red corpuscles, exaggerated in inflammatory 

 blood, may be here again noticed, i.e., their great tendency to adhere to- 

 gether in rolls or columns, like piles of coins. These rolls quickly fasten 

 together by their ends, and cluster; so that, when the blood is spread out 

 thinly on a glass, they form a kind of irregular network, with crowds of 

 corpuscles at the several points corresponding with the knots of the net 

 (Fig. 08). Hence, the clot formed in such a thin layer of blood looks 

 mottled with blotches of pink upon a white ground, and in a larger quan- 



