RED CORPUSCLES OF BLOOD. 137 



granule-cell," is found in the chyle and lymph, and occasionally in the 

 blood, of Vertebrated animals. The next stage in the history of deve- 

 lopment, is the aggregation of the granules into a distinct nucleus, and 

 the clearing up of the general cavity of the cell ; and thus is formed 

 the " colourless nucleated cell," which is the highest grade that the- 

 blood-cell attains in the Invertebrated series ; the number of such cells 

 being greater in each class, the closer is its approximation to the Ver- 

 tebrated sub-kingdom. This phase presents itself also in the blood of 

 Vertebrata, as a transition stage between the chyle- and lymph-corpus- 

 cle, and the proper blood-disk or red-corpuscle. Thus, then, we see 

 that the cells -which are found in the circulating fluid of Invertebrated 

 animals, correspond rather with those of the Chyle and Lymph of Ver- 

 tebrata, than with those which are characteristic of the Blood of the 

 latter. 



218. The next stage of development seems to consist in the acquire- 

 ment of the peculiar red colour ; and in the change of form, from the 

 spherical to the flattened or discbidal. Thus is produced the " coloured 

 nucleated cell," which is the characteristic grade of the blood-disk of 

 the Oviparous Vertebrata in general. This grade may be occasionally 

 seen in the blood of the adult Mammal, as the transition-stage between 

 the colourless nucleated cell, and the non-nucleated cells which are 

 proper to it ; but it is more easily made out in the blood of the em- 

 bryo. The non-nucleated red corpuscles which are characteristic of 

 Mammalia, are regarded by Mr. Wharton Jones as the escaped nuclei 

 of the preceding, which have undergone development into cells; but it 

 seems much more probable, that they are the same cells in a yet more 

 advanced stage of development, the nuclei having been absorbed, as 

 often happens in the case of other cells. 



219. There can be no doubt that, like all other cells, each Blood- 

 corpuscle has its proper term of life, and that it degenerates and dies 

 when this is expired ; if it were not, therefore, for the continual pro- 

 duction of new cells, in the manner just described, the Blood would 

 soon lose its due proportion of these components, since there is no 

 reason to believe that the fully-formed red corpuscle can regenerate its 

 kind, although multiplication by subdivision may take place in an 

 earlier stage of its development. When much blood has been drawn 

 from the body, the proportion of red corpuscles in the remaining fluid 

 is at first considerably lowered ; the fluid portion of the blood being 

 replaced almost immediately, whilst the floating dells require tinte for 

 their regeneration. Their amount progressively increases, however, 

 until it has reached its proper standard, provided that a due supply of 

 the materials be afforded. We shall presently see that one of these 

 materials is Iron ; and it is well known that iron administered internally 

 is an important aid in recovery from severe hemorrhages, as well as a 

 valuable remedy for certain constitutional states, in which there is a 

 diminished power of producing red corpuscles. Thus in Chlorosis, 

 under the administration of iron, the amount of red corpuscles in the 

 blood has been doubled within a short period. In the healthy state of 

 the system, the constant production, and the constant death and disin- 

 tegration, balance one another. In some instances (as in Chlorosis), 



