34 
Dr. BealEj on the Red Blood- corpuscle. 
eacli with a colourless oval " nucleus/^ and tlie so-called white 
or colourless corpuscles, which are spherical. In man and 
mammalia there are circular coloured corpuscles without a 
nucleus^and the so-called white or colourless corpuscles^ which 
are spherical. 
Now, I helieve that the ^' colourless corpuscles and the 
^^colourless nuclei^^ of the red corpuscles consist of matter in a 
living state, while there are reasons for the conclusion that the 
coloured material has ceased to exhibit vital properties. 
The outer coloured part of the oval, red, nucleated corpuscles 
of the oviparous vertebrata corresponds to the entire fully 
formed circular red corpuscles of mammalia. Of the two kinds 
of corpuscles, colourless and coloured, the former are the most 
constant. For, colourless cells resembling those in the blood 
of vertebrata exist in colourless fluids which not unfrequently 
contain fibrin. Such cells are found in the lymph and in 
the chyle, and are present in the circulating fluids of the lower 
animals, which are destitute of any cells corresponding to the 
red blood-cells of vertebrata. 
The oval form of the oviparous blood-corpuscle seems to 
depend upon the conditions under which the circulation is 
carried on, rather than upon any peculiarities in its formation ; 
for if the oval corpuscles of the frog be left at rest in a fluid 
of about the same density as themselves, they become com- 
pletely spherical, and a similar change of form occurs in the 
oval blood-corpuscles of all animals that I have examined. 
(PI. VII, figs. 16, 19, 20.) And it is well known that the 
flattened, circular, red corpuscles of mammalia readily assume 
the spherical form when placed in fluids of a certain density. 
Nor must I omit to notice here that many kinds of crystalline 
matter assume, under certain circumstances, biconcave, oval, 
and circular forms. Oxalate of lime, when it crystallizes with 
viscid matter, very frequently assumes these characters (^Illus- 
trations of Urinary Deposits,^ &c., pi. xi), and on the process 
of crystallization as modified by the presence of viscid material, 
see Mr. Eainey^s work ' On the mode of Formation of Shells,^ 
&c., 1858. 
I incline, therefore, very strongly to the opinion that the 
oval form and flattened condition, both of the outer coloured 
material and included colourless nucleus,''^ of the frog^s 
blood-corpuscle, and the biconcave flattening of the mamma- 
lian red corpuscle, are due to the consistence of the material 
entering into its composition, to the movements of the blood- 
corpuscles, and to the action of fluids and gases upon them, 
and that therefore they must not be regarded as structural 
or morphological characters. 
