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TEXT-BOOK OF PHYSIOLOGY 



and changes to a dark red color to which the term "laky" has been given. 

 The mechanism by which the hemoglobin becomes dissociated and dis- 

 charged from the corpuscle by these agents is unknown. The disinteg- 

 ration of the corpuscle and the diffusion of the hemoglobin into, and its 

 solution by the surrounding medium, is termed hemolysis and the agents 

 by which it is produced are termed hemolytic agents. 



CHEMIC COMPOSITION OF RED CORPUSCLES 



When analyzed chemically the red corpuscles are found to consist of 

 water 65 per cent, and solid matter 35 per cent. The solids, moreover, have 



been found to consist of a pigment hemo- 

 globin 33, protein 0.9, cholesterin and 

 lecithin 0.46, and inorganic salts (chiefly 

 potassium phosphate and chlorid and 

 sodium chlorid) 1.4 per cent, respectively. 

 Of the total solids the hemoglobin con- 

 stitutes about 94 per cent. 



Hemoglobin. In the normal condi- 

 tion of the corpuscle the hemoglobin is in 

 an amorphous condition and is com- 

 bined in some unknown way with the 

 stroma. 



When hemoglobin is decomposed in 

 the absence of oxygen it undergoes a 

 cleavage into a protein, globin, and an 

 iron-holding pigment, hemochromogen, 

 which constitutes about 4 per cent, of 

 the molecule. If a solution of hemo- 

 chromogen be exposed to air it absorbs 

 oxygen and is converted into hematin. 

 This latter compound can also be de- 

 rived directly from hemoglobin by the 



action of acids and alkalies. It is to the 

 FIG. 96. CRYSTALLIZED HEMO- r i i_ * 



GLOBIN. a, b, Crystals from venous blood presence ot hemochromogen in combma- 

 of man. c. From blood of cat. d. Of tion with the protein globin that the 

 marmot ' f ' Of hemoglobin is indebted for its power of 



absorbing and carrying oxygen. 

 If blood which has been rendered laky, by water or any other of the 

 known agencies, be allowed to evaporate slowly, the dissolved hemoglobin 

 undergoes crystallization. The rapidity with which the crystals form varies 

 in the blood of different animals under similar conditions. According to the 

 ease with which crystallization takes place, Preyer has classified various 

 animals as follows: (i) Very difficult calf, pigeon, pig, frog; (2) difficult 

 man, monkey, rabbit, sheep; (3) easy cat, dog, mouse, horse; (4) very easy 

 guinea-pig, rat. 



The hemoglobin crystals vary in shape according to the blood from 

 which they are obtained (Fig. 96). Those obtained from the guinea-pig 

 are tetrahedral; those from man and most mammals are prismatic rhombs; 

 those from the squirrel are in the form of hexagonal plates. Notwith- 



