300 THE BLOOD, [CHAP. XXVII. 



In the Invertebrate classes, corpuscles exist which are in close analogy with 

 those of the Vertebrata, but differ from them in several particulars (Fig. 178). 

 They are nucleated cells, some of which contain within them numerous granules 

 which conceal the nucleus ; some of these corpuscles, according to Mr. Wharton 

 Jones, are, upon their first removal from the body, of an elongated oval form, 

 and others spindle-shaped. Their size does not exceed ^th of an inch in their 

 long diameter, nor 3S |j th in the short. In most of the classes the particles do 

 not exhibit any indication of colour, although they contain some of the ingre- 

 dients of hematine ; in a few, however, slight traces of colour are present.* 



Of the Structure of the Red Corpuscles. The structure of the red 

 corpuscle of most of the vertebrata may be readily demonstrated 

 in the blood of Reptilia that of the frog, for instance. It is dis- 

 tinctly a nucleated cell consisting of a delicate cell membrane, 

 within which is a granular nucleus, which may be rendered more 

 distinctly granular by acetic acid (Fig. 176, B). The nucleus is 

 globular and much smaller than the cell, and the interval between 

 the inner surface of the latter and the outer surface of the former 

 is filled by fluid which holds the colouring matter in solution. 

 Corpuscles of this kind floated in pure water become distended by 

 the endosmosis of it, burst and give exit to their nuclei, while the 

 shreds of the cell-membrane are scattered in the fluid. 



It cannot be shown satisfactorily that the biconcave circular cor- 

 puscle of human blood, and of that of mammalia, is of the same 

 structure as this, because it cannot be demonstrated to consist of cell 

 and nucleus. If it be, as the blood-corpuscles of birds, reptiles, and 

 fishes undoubtedly are, a nucleated cell, the obscurity of its nucleus 

 is probably due to one of two causes; either it is so large as 

 accurately to fill the cell, leaving no space between the outer surface 

 of the one and the inner surface of the other, or it is so extremely 

 minute as completely to elude our means of observation. 



Mr. Wharton Jones supposes that the mammalian red corpuscle is 

 a nucleus, the cell of which had existed only in the earlier stages of 

 development. Kblliker, on the other hand, affirms that the nucleus 

 disappears while the cell- wall is persistent. All that microscopic 

 examination with the highest powers and the best instruments 

 shows respecting the structure of this corpuscle is, that it consists 

 of a delicate membrane, enclosing a semifluid material, impreg- 

 nated with the proper colouring matter of the blood ; and that this 



* Mr. Wharton Jones' papers in the Phil. Trans, for 1846, "On the blood- 

 corpuscle considered in its different phases of development in the animal 

 series," contain an account of a careful examination of those particles, and 

 may be referred to with advantage by all who are engaged in the study of 

 this most interesting subject, 



