Blood-corpuscles of A. tridactylum, &c. By Dr. Schmidt. 105 
structure, as well as in most chemical and physical properties, those 
of the Amphiuma; it is only in size that a very considerable 
difference exists between them. For while in the Amphiuma the 
length of these bodies ranges from about to mm., they 
only attain a length of yf^Tj to yf-^^ mm. in the Frog. And even 
in the latter their size depends to a certain extent upon the average 
size of the particular species. Thus I have found the largest cor- 
puscles in the blood of those giants among the frogs (Fig. 48, a 
and h), the bull-frogs, which attain a length of from twelve to 
thirteen inches, measured from the nose to the toes. 
The difference of colour which I described to exist between the 
border and the rest of the blood-corpuscle of the Amphiuma, may be 
equally observed, not only on the blood-corpuscles of the Frog and 
other Amphibia, but also on those of Birds. While the main part 
of the corpuscle, as will be remembered, is of a dirty yellow, the 
border is distinguished by a greenish tint ; and although there 
exists no distinct line of demarcation between the two colours, 
representing an inner contour, this nevertheless appears under 
certain conditions, just as in the case of the blood- corpuscles of the 
Amphiuma. The various changes of form which we have been 
noticing to take place in the latter in their fresh condition, and 
which depend on a contraction of the protoplasm, do not occur to 
such an extent on the fresh blood-corpuscles of the Frog. Not 
unfrequently, however, corpuscles are met with, in which by a con- 
traction of the protoplasm this part of the corpuscle has in some 
places become separated from the membraneous layer. Here a 
vacuum is left between the latter and the retracted protoplasm 
(Fig. 49), in consequence of which the membraneous layer mani- 
fests itself by a double contour. By an oblique illumination the 
inner contour, representing the place of separation of the membra- 
neous layer from the protoplasm, is rendered darker and more 
distinct. 
This phenomenon, frequently observed on fresh coloured blood- 
corpuscles of the Frog, teaches us that, under certain conditions still 
unknown, a separation of the protoplasm from its membraneous 
layer may occur, and extend over a greater or smaller space. Now, 
if such a separation, accompanied by a simultaneous contraction of 
the protoplasm upon the nucleus, occurs in a number of places, 
representing regular intervals between a number of small points, at 
which the union of the protoplasm with its membraneous layer 
remains undisturbed, that peculiar appearance or star-like form of 
the blood-corpuscle is produced which has given rise to those 
theories concerning the structure of these bodies, spoken of before. 
Such forms are said to be specially obtained in the blood of 
x^mphibia by the aid of water, or by a 2 per cent, solution ot 
boracic acid. Though I have not succeeded in producing these 
