PROPERTIES OF THE BLOOD. 431 



alcohol that contain alkalies or acids, whence it may be supposed to unite with 

 these, like albumen, as an acid or a base. In composition, however, it differs 

 considerably from both protein and albumen ; its formula being 44 c, 22 H, :J 

 N, 6 o, with a single proportional of iron. When burned, it yields a notable 

 quantity of peroxide of iron ; and one atom of this is considered to be present 

 in combination with one of the animal compound, which is analogous to protein. 

 The red colour is not due, however, as formerly supposed, to the presence of 

 this peroxide ; for M. Scherer has recently found, that the metal may be 

 entirely dissolved away by the agency of acids, and that the animal matter, 

 afterwards boiled in alcohol, colours the spirit intensely red. The globulin, 

 which is the principal constituent of the corpuscles, has not yet been isolated ; 

 but from its properties in combination, it is inferred to differ but little from 

 protein. It may perhaps be doubted, whether these two principles have a 

 separate existence ; or whether they are not rather results of the chemical 

 processes employed to obtain them. When the blood-discs are separated from 

 the other constituents of the fluid, and are immersed in water, they soon absorb 

 so much as to become globular ; and the continuance of the endosmose occa- 

 sions the diffusion of their contents (by the rupture of the capsule) through 

 the water, in which the greater part dissolves. This solution exhibits the 

 same changes of colour under the influence of oxygen, acids, saline matter, 

 &c., as the blood undergoes in similar circumstances ( 542). When it is 

 heated, the matter of the globules is coagulated and forms an insoluble pre- 

 cipitate ; both in its soluble and coagulated states, it exhibits similar effects 

 with reagents, as does albumen in the same conditions. 



574. The question of the origin of the red Blood-corpuscles is a very in- 

 teresting one, and cannot yet be regarded as completely determined. That 

 they are to be regarded as nucleated cells, conformable in general character 

 with the isolated cells, which constitute the whole of the simplest Plants 

 ( 555), and having each an independent life of its own, there can now be no 

 reasonable doubt. From this we should infer that they have the power of 

 reproducing themselves ; and the recent observations of Dr. Barry and other 

 Microscopists have confirmed the statement long ago made to that effect by 

 Leeuwenhoek. The first change which takes place is the appearance of 

 delicate radiating lines between the nucleus and the periphery ; dividing the 

 disc into several segments, usually six in number (Fig. 22, Plate I.). The 

 margin is soon observed to become crenated, by indentations at corresponding 

 points ; and these indentations become deeper, until a complete separation 

 takes place, forming six young cells or discs (, b, c, d, e). It is next to cer- 

 tain that these are developed within the parent cell or disc, from some of the 

 granules on the margin of its nucleus ; just in the same manner as rings of 

 cells will be hereafter described ( 745) as arising from the Germinal Spot. 

 From this fact, connected with what has been already stated of the continual 

 decomposition of the blood-discs ( 572), we may infer that each cell has a 

 determinate period of existence ; and that whilst some are decaying from age, 

 their place is being supplied by young ones in process of growth. Between 

 the small newly-generated disc, and the full-sized corpuscle, we should expect 

 to find every intermediate size ; and this is exactly what presents itself. That 

 the corpuscles may be generated with great rapidity under peculiar circum- 

 stances, will hereafter appear ( 594) ; and their amount may undergo a rapid 

 diminution also, without any evident abstraction of them from the circulating 

 fluid. Appearances have been seen by Wagner, Gulliver and others, in the 

 blood of Batrachia, which seem to indicate that the Colourless corpuscles 

 ( 577) serve as the nuclei of cells, which, when fully developed, may become 

 Red blood-discs ; but in the Mammalia it is scarcely possible to imagine that 

 this can occur ; since the diameter of the colourless corpuscles is very con- 



