THE CIRCULATORY SYSTEM, 



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jmscles : including mao, and qther mammals, except the camel 

 family, which have \val t non-nucleated red blood-cells. 



Human blood-cells : TV, color- 

 less corpuscle, surrounded by 

 red cells ; those at r exhibit a 

 partially-formed rouleau. 



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Since an oval_coruscle on""*b>eing subjected to certain reagents 

 may present a circular outline, the presence or absence of a nucleus 

 offers the most reliable means of differential diagnosis between 

 mammalian and other bloods. ri^^^c^Ct^^ ^Lu^^^^^ 



The human colored blood-cell, or erythrocyte, is a small disk, 

 about 8 PL in diameter, and exhibiting individually a faint greenish- 

 yellow tinge. The well-known color of the 

 blood appears only when great numbers of 

 these corpuscles are massed ; the term ' ' red' ' 

 conventionally applied to these elements is, 

 strictly regarded, incorrect and less appro- 

 priate than ' ' colored. ' ' The two surfaces of 

 the blood-disk are not perfectly flat, the centre 

 of the corpuscle being slightly biconcave, 

 while its edges are rounded, biconvex, and 

 somewhat thickened : in consequence of this 

 peculiar "biscuit" form, all planes of the 

 corpuscle are not seen accurately focused at 

 one time, the centre usually appearing either darker or lighter than 

 the marginal parts of the cell, depending upon the focal adjustment. 



The jtructure of the colored blood-corpuscles is still a subject of 

 discussion. According to the generally accepted view, the cor- 

 puscles consist of two parts : (a) the transparent, colorless, apparently 

 homogeneous, and plastic strorna, extensible and pliable to a high 

 degree, and (ft) the c6Io7m^matter7"or haemoglobin, which is held 

 within, and uniformly distributed throughout, the former. This 

 conception of the corpuscle assumes the presence of a uniform 

 though highly flexible stroma-mass of definite form, colored by^the 

 imbibition of the soluble haemoglobin. On the other hand, the 

 behavior of these elements when treated with water, upon the 

 addition of which the corpuscles swell, lose the discoidal form, and 

 become globular, as well as the suggestive appearances following the 

 staining with aniline of such bleached corpuscles, the outlines of the 

 cells then showing as distinct rosy rings, offers strong arguments, in 

 the opinion of not a few, for the belief that the rea corpuscles are 

 minute sacs, consisting of a limiting membrane and the colored fluid 

 contents. 



The nuclei of the red cells, when present, lie embedded within 

 the colored stroma ; in perfectly fresh or circulating corpuscles they 

 are made out with great difficulty, since they possess a refractive 

 index almost identical with that of the other parts of the cell. After 

 reagents, or after the expiration of some minutes, the nuclei become 



