STRUCTURE AND COMPOSITION OF RED CORPUSCLES. 207 



will then burst ; and their contents will be diffused through 

 the surrounding fluid, whilst their membranous walls will 

 subside to the bottom. On the other hand, if the liquor 

 sanguinis be rendered denser than the fluid in the blood- 

 discs, as by the admixture of gum or syrup, the latter will 

 pass towards it, and the cells will become still more flattened, 

 and more or less completely emptied. The flexibility and 

 elasticity of the blood-discs are well seen, in watching (with 

 a microscope) its flow through the minute vessels ; for if one 

 of them meets with an accidental obstruction to its progress, 

 its form becomes accommodated to that of the space left for 

 it to pass, and it makes its way through a very small aperture, 

 recovering its usual form immediately afterwards. 



232. The Eed Corpuscles differ considerably in chemical 

 composition from the liquid in which they float. Of the 

 solid residue obtained by drying, about one-eighth is formed 

 by their cell-walls, the remainder being yielded by the cell- 

 contents. The latter portion seems to consist chiefly of a 

 mixture of two components, which have been named globulin 

 and hcematin. The former is a colourless substance, nearly 

 allied to albumen in composition, but differing from it in 

 some of its reactions ; its most characteristic peculiarity, how- 

 ever, being its power of crystallizing. Its crystals, the form 

 of which varies in different animals, are usually tinged deeply 

 with hsematin, from which they cannot easily be freed. The 

 composition of hsematin, to which alone the colour of the red 

 corpuscles (and consequently of the whole mass of the blood) 

 is due, is notably different from that of the albuminoid 

 compounds ; the proportion of carbon to the other components 

 being much greater, and a definite quantity of iron being an 

 essential part of it. This iron, in a certain state of oxidation, 

 has been supposed to be the source of the red colour; but 

 such is certainly not the case ; and this hue must be, like the 

 colours of Plants, a peculiar attribute of the organic compound 

 which presents it. Besides their globulin and haematin, the 

 red corpuscles contain a certain proportion of fatty and 

 mineral matters. The former, which are united with phos- 

 phorus, are of a kind which are scarcely traceable in the 

 liquor sanguinis ; and the latter are remarkable as having 

 potass for their principal base, whilst the base of the salts of 

 the liquor sanguinis is chiefly soda. Hence it appears that 



