Blood-corpuscles of A. tridactylum, &c. By Dr, Schmidt. 117 
Now the question arises : Does the inner contour represent that 
delicate shade, which I described on the fresh unaltered blood- 
corpuscle as representing the inclination, passing from its thick 
convex marginal to its thin and concave central portion ; or is it in 
reality the inner contour of an existing membraneous layer, made 
visible by the solution of the protoplasm within it, as in the case 
of those large nucleated coloured blood-corpuscles of the Amphibia ? 
Let us try to solve this question. A close examination of the front 
i surface of one of these blood-corpuscles, affected by the action of the 
water, will reveal that the diameter of the central portion of the 
corpuscle has increased, while that of the peripheral portion, 
representing its convexity, appears much narrower than in the 
fresh specimen. From this we may judge that there must have 
been some loss of substance in the interior of the blood-corpuscle, 
I causing it to collapse in thickness. In other words, the proto- 
plasm, with the exception of a thin stratum or layer forming the 
surface of the corpuscle, was dissolved by the action of the water, 
giving to the whole the character of a cell. Thus the changes 
brought about by the action of water in the non-nucleated blood- 
corpuscles of Man are similar to those observed under the same 
, conditions in the large nucleated corpuscles of the Amphibia. No 
' true cell-membrane can he discovered in their normal condition; 
while in either case a delicate stratum seems to exist at the 
surface of the corpuscle, which, being denser in its nature than the 
rest of the protoplasm, resists longer the solvent action of the water, 
I and in consequence manifests itself in the form of a delicate 
double contour. In the human blood-corpuscle this membraneous 
, layer, as we have called it before, must be exceedingly delicate, as 
I no trace of it can be discovered on the fresh unaltered specimen. 
[ It is probable, however, that its invisibility in the fresh condition 
is owing to the circumstance of the peripheral portion or margin of 
the human blood-corpuscle being perfectly rounded, while the 
margin of the blood-corpuscle of the Amphibia is almost flat, and 
proportionately thinner, in consequence of the bi-convexity of the 
whole disk. 
But the fact that a cavity is produced in the interior of the 
blood-corpuscle by the action of water, is rendered still more 
apparent when a specimen is examined in its exact profile, as may 
be seen in Fig. 62, h, where the delicate median line represents the 
cavity. This can only be done while the corpuscle is floating in 
the water, and slowly turning around its horizontal axis. When 
the corpuscles, after being altered by the action of water, are 
treated with a weak solution of chromic acid, the double contour 
appears still more distinct. 
The blood-corpuscles of Man do not swell or assume a spherical 
form (as I myself several years ago erroneously believed) by the 
