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 Red 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 hsematin, 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 
