J40 HANDBOOK OF PHYSIOLOGY. 



disintegration of the colorless corpuscles. This supposition is certainly 

 plausible, and, if it be a true one, it must be assumed either that the 

 living blood-vessels exert a restraining influence upon the disintegration 

 of the corpuscles in sufficient numbers to form a clot, or that they ren- 

 der inert any small amount of fibrin ferment, which may have been set 

 free by the disintegration of a few corpuscles; as it is certain, firstly, 

 that white corpuscles must from time to time disintegrate in the blood 

 without causing it to clot; and, secondly, that shed and defibrinated 

 blood which contains blood corpuscles, broken down and disintegrated, 

 will not, when injected into the vessels of an animal, under ordinary 

 conditions, produce clotting. There must be a distinct difference, 

 therefore, if only in amount, between the normal disintegration of a few 

 colorless corpuscles in the living uninjured blood-vessels and the abnor- 

 mal disintegration of a large number which occurs whenever the blood 

 is shed without suitable precaution, or when coagulation is unrestrained 

 bv the neighborhood of the living uninjured blood-vessels. 



The Blood Corpuscles. 



There are two principal forms of corpuscles, the red and the white, oi> 

 as they are now frequently named, the colored and the colorless. In the 

 moist state, the red corpuscles form about 45 per cent by weight, 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 a 

 circular, biconcave discs with rounded edges, from j^Vir ^ 40*00 inch in 

 diameter 7/t to 8j", and T2 ^ 00 inch or about 2 ( in thickness, becoming 

 flat or convex on addition 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 all parts by a red coloring matter 

 termed hcemoglobin. The stroma is tough and elastic, so that, as the 

 corpuscles 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, although sometimes applied, is scarcely applicable to the red blood 

 corpuscle; it must be considered, if not solid throughout, yet as having 

 no such marked difference 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 substance, and the coloring-matter uni- 

 formly pervades this ; but at the same time it is probable that the con- 

 sistence of the peripheral part of the protoplasm is more solid than that 

 of the more central mass. 



