STRUCTURE OF THE COLOURED BLOOD CORPUSCLES. 



211 



light on the nature of this membrane. For it is not easy to understand why they 

 should produce their particular effect unless the membrane were capable of being 

 Dartly or entirely dissolved by them, and this would indicate that it is largely of 

 a fatty nature. Whether it is a pellicle of true fatty substance, or, as is more 

 probable, a fat-like material into the composition of which the lecithin, cholesterin 

 and proteid, which are described as composing the so-called stroma, enter, cannot here 

 be discussed. 



Various other phenomena which have been noticed in connection with the action of reagents 

 and varying external conditions upon the red corpuscles point to the same conclusion, viz. 

 that the external envelope of the red corpuscle is composed of a material having the physical 

 characters of fats. A heat of 52 C. causes the coloured corpuscles to extrude globular pro- 

 cesses and beaded filaments which may attain a rela- 

 tively considerable length, and which eventually break 

 off from the main substance of the corpuscle and form 

 coloured globules in the fluid. A further increase of 

 temperature to 60 C. sets free the haemoglobin, 

 and produces the complete disappearance of the 

 corpuscles. Here we may suppose the fatty pellicle 

 to become softened and eventually completely melted 

 under the action of the increased temperature, thus 

 permitting of the partial and eventually of the com- 

 plete flowing out of its contents. 



Almost any fluid which has a slight solvent action 

 upon fats also causes an extrusion of the haemoglobin 

 often with disappearance of all sign of the stroma or 

 membrane ; this is the case with solutions of the bile 

 salts. Dilute alcohol in the form of sherry wine has been 

 noticed to produce at first the extrusion of filaments 

 like those caused by heat (Addison) ; and this may be 

 supposed also to be due to the softening or incomplete 

 solution of a fatty pellicle. The envelopes of the 

 corpuscles (" stromata") after complete decolorization 

 with water or dilute acids, stain faintly, but charac- 

 teristically of the presence of fatty substance, when 

 treated with osmic acid. Finally, the presence of a 

 fatty pellicle would of itself, as above pointed out 

 (p. 209), furnish a sufficient explanation of the other- 

 wise obscure phenomenon of rouleau-formation. 



It has often been urged against the existence of a 

 membranous envelope to the corpuscles that such an 

 envelope when mechanically ruptured, as by pressure 

 upon the corpuscles, should show signs of the gap 

 through which the contents have escaped. This is by 

 no means necessary, however, for in the case of a thin 

 fatty pellicle such as that the existence of which is 

 here assumed, the torn edges would immediately tend 

 to come together again after rupture, and would then 

 show no indication of the breach of continuity. A simi- 

 lar explanation may be given of the fact that a cor- 

 puscle may sometimes be cut into two, as when a needle 

 is drawn sharply across a preparation of newt's blood 

 upon a glass slide, without the coloured contents 

 escaping from the two separated parts ; in this case 

 the pressure of the needle-point has at the same time 

 that it severed the corpuscle brought together the oppo- 

 site edges of the cut pellicle, and thus prevented the 

 escape of the contents. 



Blood in which the haemoglobin has been dissolved 

 out from the corpuscles has lost its opaque appearance, 

 and has acquired a transparent laky tint ; the change 



depends upon the fact that the colouring matter when dissolved in the serum and forming a 

 homogeneous layer, interferes less with the transmission of light than when occurring in 

 scattered particles. 



Haemoglobin after being thus separated from the blood-corpuscles is prone to undergo 



Fig. 243. BLOOD-CRYSTALS, MAGNIFIED. 



1, from human blood ; 2, from the 

 guinea-pig ; 3, squirrel ; 4, hamster. 



X 



IMK 



f< 



T 



Fig. 244. HJKMIN CRYSTALS, MAGNIFIED 

 (from Preyer). 



