176 ROBERTS, ON BLOOD-CORPUSCLES. 
glass, and permitting a little blood to insinuate itself into the 
solution under the microscope. As the blood flowed in and 
mingled with the tannin, the corpuscles were observed gra- 
dually to enlarge, and then suddenly, without previous warn- 
ing, to shoot out the projection. As a rule, it does not 
appear to grow afterwards. The phenomenon was finely seen 
in the defibrinated blood of the fowl after it had been allowed 
to sink through a column of syrup (sp. gr. 1025) im a test- 
tube. Fowl’s blood washed in this way was mixed, in a little 
glass, with about five times its volume of the tannin solution, 
and a drop immediately put under the microscope. The 
discs first enlarge and become rounded, and the central nu- 
cleus comes into view. In thirty or forty seconds the pullu- 
lation begins ; and each corpuscle, with instantaneous rapidity 
and without previous sign, throws out its bud. The dise 
itself suffers not the least disturbance during this act; it pre- 
serves its symmetry unchanged, as if it had no concern, beyond 
that of proximity, with the sudden apparition on its surface. 
No visible rupture of the cell-wall tock place. The cir- 
cular outline of the latter could sometimes be distinctly fol- 
lowed through the projection (fig. 2, ¢); and as the altered 
corpuscles revolved in the field of the microscope, the projec- 
tion appeared to be organically connected with it, but to 
form no part of its cavity. In the human blood-dises the 
application of acetic acid, soon after the tannin, caused, on 
two occasions, the pullulations gradually to subside, and 
finally to disappear, and then the disc resumed its original 
circular outline. I failed to produce this “redux” effect in 
the fowl; and did not always succeed with human blood, 
probably because the change produced by the tannin had 
gone too far. 
The modification noted under the term “ hooded” appear- 
ance depends, I believe, upon secondary conditions of con- 
centration and quantity of the tannin solution in comparison 
to the blood. When the hooded condition has been watched 
in the act of occurrence, it was noticed that the outer hood 
was shot out first, and instantly after this the highly refrac- 
tive vesicular body made its appearance within. The con- 
tents of the hood (excluding the vesicular body) appeared 
usually to refract the light lke the body of the cell, or even 
less strongly ; sometimes, however, more strongly. 
The effect of tannin did not cease with the preduction of 
the elevations just described. At first the cells and their 
projections preserved their elasticity; but after a while (a 
few minutes, or several hours, according to the proportions 
used) the corpuscles and their projections become solid, and 
