68 BLOOD-CORPUSCLES. 
the blood-corpuscles to be vesicles.' He relied especially upon 
the manner in which they were acted on by water, whereby 
they lose their colouring matter, swell, and become round, and 
under which circumstances he frequently saw the nucleus roll 
about within the round and very transparent vesicle. The last 
fact would of itself be sufficiently conclusive. JI have not as 
yet observed this fact; on the contrary, in most instances the 
nucleus decidedly adheres to the internal surface of the wall 
of the vesicle, eccentrical as in all cells, though it may pro- 
bably also sometimes become detached. The fact, however, of 
the blood-corpuscles becoming swollen and round, renders their 
cellular nature highly probable. If the envelope (hiille) of the 
blood-corpuscle were not a flattened vesicle, it might indeed 
lose its colour and swell in water, but it would retain its flat 
form, like a sponge when filling with fluid. The circumstance 
of the nucleus remaining on the wall during the swelling of 
the blood-corpuscle in water is no accidental appearance ; for 
even in the round blood-corpuscles of a chick, forty-eight 
hours after the commencement of incubation, when they were 
not as yet flattened, I found that the nuclei, which were also 
circular, were not placed in the centre, but lay eccentrical upon 
the internal surface of the wall. The cellular nature of the 
blood-corpuscle, and the signification of its separate parts 
scarcely appear to admit of doubt when regarded in connexion 
with the whole of this mvestigation. It is a flattened cell fur- 
nished with a cell-nucleus, which is fixed to a spot on the in- 
ternal surface of the cell-membrane. The size of the cell as 
compared with the nucleus is not the same in all corpuscles ; 
that of the nucleus is much more constant. The nucleus of 
some blood-corpuscles of frogs which had swollen in water, also 
appeared to me in some instances to be hollow. It also loses 
its flatness in water, but retains its oval figure. I have 
1 [This is clearly an oversight as Hewson not only demonstrated their vesicular 
nature, and called them vesicles, but accurately described their becoming “ changed 
from a flat to a spherical shape,” on the addition of water to the blood, and the falling 
of the nucleus “ from side to side in the hollow vesicle, like a pea in a bladder.” See 
‘Philosophical Transactions,’ 1773, vol. lxiii, Part Il; or, ‘Experimental Inquiries,’ 
Part III, being ‘a Description of the Red Particles of the Blood,’ &c., &e. (published 
after his death), edited by Magnus Falconar, London, 1777; also the very valuable 
republication of Hewson’s Works by the Sydenham Society, edited by George Gulliver, 
Esq., where the reader is particularly referred to pp. 220, 221.—Trans. ] 
a ele i i i it th 
—— 2 
_ 
ot (22 epee 20) eo 
PVP Gar; ot ce eae es 
