34 GENERAL ANATOMY. 



We may now consider the constituents of the blood in another way. If a drop 

 of blood is placed in a thin layer on a glass slide and examined under the micro- 

 scope, it will be seen to consist of a number of minute bodies or corpuscles floating 

 in a clear fluid ; and, on more minute examination, it will be found that these cor- 

 puscles are principally of two kinds. The one, greatly preponderating over the 

 other in point of numbers, is termed the colored corpuscle ; the other, fewer in 

 number and less conspicuous, is termed the colorless corpuscle. From this we 

 learn that blood is a fluid holding a large number of corpuscles of two varieties m 

 suspension. The fluid is named liquor sanguinis or plasma, and must not be con- 

 fused with the serum spoken of above in connection with the coagulation of the 

 blood. It is serum and something more, for it contains one at least of the 

 elements or factors from which fibrin is formed. The relation of these various 

 constituents of blood to each other will be easily understood by a reference to the 



subjoined plan : 



f Colored ^ 



Corpuscles { Golorless 1 



( Fibrin j 

 *- Liquor Sanguinis < 



( Serum 



The blood-corpuscles, blood-disks, blood-globules are, as before stated, of two 

 kinds : the red or colored, and the white or colorless corpuscles. The relative 

 proportion of the one to the other has been variously estimated and no doubt 

 varies under different circumstances. Thus venesection, by withdrawing a large 

 proportion of the red globules, and by favoring the absorption of lymphatic fluid 

 into the blood, greatly increases the relative proportion of the white corpuscles. 

 Klein states that in healthy human blood there appears to be one white corpuscle 

 for 600-1200 red ones. The proportion of corpuscles, colored and colorless com- 

 bined, to liquor sanguinis is in one hundred volumes of blood about thirty-six 

 volumes of the former to sixty-four of the latter. 



Colored corpuscles when examined under the microscope are seen to be circular 

 disks, biconcave in profile, having a slight central depression, with a raised bor- 

 der (Fig. 1, b\ When viewed with a moderate magnifying power, this central 



depression looks darker than the edge. When exam- 

 ined singly by transmitted light, their color appears to 

 be of a faint reddish-yellow when derived from arterial 

 blood, and greenish-yellow in venous blood. It is to 

 their aggregation that blood owes its red hue. Their 



size varies sli gh tlv even in tne same ^ r P f blood, out 

 -it may be stated that their average diameter is about 



rid. i-Humau blood-corpus- WoT of an inch their thickness about ^ko, or nearly 

 des. a. seen from the surface, one-quarter of their diameter. .Besides these, especially 

 inSeauT^RenVed^phlr 1 in some anaemic and diseased conditions, certain cor- 

 ^t^-SS 81 -/. M<5dSSSS puscles are found of a much smaller size, about one- 

 shrunk by evaporation. third or half the size of the ordinary one. Inese, 



however, are very scarce in normal blood. The number of red corpuscles in the 

 blood is enormous; between 4,000,000 and 5,000,000 are contained in a cubic 

 millimetre. Power states that the red corpuscles of an adult would present an 

 aggregate surface of about 3000 square yards. Human blood-disks present no 

 trace of a nucleus. They consist of two parts : a colorless envelope, or investing 

 membrane, which is composed largely of fatty material ; and a colored fluid con- 

 tents, which is a solution of a substance named haemoglobin. Hcemoglobin is a 

 proteid compound of a very complex constitution, the haemoglobin of the horse 

 having the formula C 712 H 1130 N 214 S 2 Fe0 245 . It has a great affinity for oxygen, and 

 when removed from the body crystallizes readily under certain circumstances. 

 It is readily soluble in water, and the addition of this fluid to a drop of blood 

 speedily dissolves out haemoglobin from the corpuscle. 



