ROBERTS, ON BLOOD-CORPUSCLES. — 175 
Of fish, the dace, minnow, and carp, were examined. The 
tannin solution produced a similar effect to that seen in the fowl 
—with this difference, that a large number of corpuscles had 
Blood of fowl after the action of tannin. 
two projections instead of one. In the carp double and single 
projections occurred in about equal proportions; in the 
minnow double projections were all but universal. The 
second projection was situated sometimes at the opposite pole 
of the disc, sometimes in near proximity to its fellow, or at 
any point between. Very rarely a third projection was scen 
in the dace. 
In the blood of the frog there was a strong tendency to the 
indefinite multiplication of the projections; two, three, four, 
and even five, would rise in succession on the surface of the 
dise. It appeared, too, not unfrequently as if the entire outer 
membrane of the cell was detached from the parts beneath, and 
raised into eight or ten unequal elevations, giving the outline 
of the disc an irregularly crenate appearance.* 
The formation of these singular projections, or pullulations, 
on the blood-dises could be watched without difficulty by 
placing a drop of the tannin solution beneath the covering 
* There is a certain adjustment of the proportions between the tannin 
solution and blood required to bring out the effects described in this paper ; 
but the proper proportions are, practically, very easily found after a few 
trials for each kind of blood. In mammalian blood one drop of blood mixed 
in a conical glass with four or five of the solution generally answered per- 
fectly. Any considerable excess of blood or solution above these proportions 
caused destruction of the corpuscles. 
