58 Transactions of the Boyal Microscopical Society. 
A number of years ago, histologists began to deny the existence 
of an enveloping membrane in the coloured blood-corpuscles, and 
maintained that the latter consisted of protoplasm only, united with 
a colouring material, the hcemogldbin. In support of this view, 
they referred to the bi-concave form of the blood-corpuscles of the 
Mammalia, and also to the great elasticity which all blood-corpuscles 
show they possess in assuming almost any form to adapt themselves 
to the various curvatures and angles of the smallest capillary vessels 
through which they have to pass ; properties which could not be 
possessed by a vesicular body. The behaviour of the blood-cor- 
puscles towards various reagents, and finally, the impossibility of 
demonstrating this enveloping membrane, were also adduced to 
prove its absence. 
But while these histologists, by denying the existence of an 
enveloping membrane, were endeavouring to make the structure of 
these blood-corpuscles appear of a more simple nature, others, espe- 
cially in Germany, propounded theories, according to which the 
construction of these bodies appears quite complex. 
In explanation of the various phenomena manifested by the 
coloured blood-corpuscles, several hypotheses regarding their struc- 
ture were advanced from time to time. Thus Kollett, denying the 
existence of the membrane, looks upon them as mainly consisting of 
a certain stroma, to which they owe their peculiar mechanical pro- 
perties.* This view is based upon the examination of the colourless 
remains of the blood-corpuscles of the guinea-pig, horse, and dog, 
which he deprived of their colouring matter by a peculiar freezing 
and thawing process. Kuehne, another opponent of the membrane, 
strongly endorses the view of Eollett. 
Another well-known hypothesis, founded upon certain appear- 
ances observed on the blood-corpuscles of the Triton, after having 
been treated with a 2 per cent, solution of boracic acid, is that of 
Bruecke. According to it, the nucleated blood-corpuscle consists 
of two parts. The one of these, representing a porous body, of a 
motionless, very soft, colourless, and transparent substance; the 
other a living organism, the central portion of which forms the 
nucleus, filling up the pores of the former, and, with the exception 
of the colourless nucleus, containing the haemoglobin. The colour- 
less porous substance, Bruecke named oihoid, the other part zooid. 
By the contraction of the latter from the former, he tries to explain 
the occurrence of those appearances observed on the blood-corpuscles 
of some Amphibia, consisting in the entire or partial retraction of 
the coloured contents upon the nucleus, and assuming in the latter 
case the form of a star, as represented by Eollett, on p. 286 of 
Strieker’s ‘ Handbuch der Lehre von den Geweben, &c.’ 
This hypothesis, fanciful as it is, does not explain the pheno- 
* Kuehne, ‘ Lehrbuch der Physiolog. Oliemie,’ p. 190. 
