22 
Addison_, on Blood-corpuscles, 
line ajid saline fluids^ are like forms d, fig. 3, which are pro- 
duced in acid liquids, the only difference between them being 
that those observed in alkaline are deeper coloured than those 
in acid fluids. Corpuscles of this form b, fig. 2, and d, 
fig. 3, are incapable of regaining the normal form. Ulti- 
mately, in alkaline fluids, the forms 6, fig. 2, burst open, 
and the corpuscles are wholly dissolved; in acid liquids 
(fig. 3, d) they sometimes burst open suddenly, and some- 
times suddenly increase in size, the contents of the corpus- 
cles become colourless, and the enlarged capsules, with a 
granular matter within them, have very much the appearance 
of the white corpuscles of the blood (fig. 3, e) . 
Dissolve a grain of common salt and half a grain of bicar- 
bonate of soda in two fluid drachms of water, mix this 
solution with half a fluid ounce of good sherry wine, and 
filter. This liquid produces the tailed corpuscles (fig. 4). A 
small drop of blood and an equal quantity of the vino-saline 
mixture must be placed side by side on a slip of glass, so that 
their edges may mingle when a thin covering-glass is dropped 
upon them. In about five or ten minutes numerous corpus- 
cles, where they have floated out in the liquid, will be seen 
throwing out matter from their interior, two, three, four, 
or more minute molecular particles fringing their circum- 
ference. Some of these molecules separate from the cor- 
puscles and float in the fluid, others elongate into tails, which 
wave about with a tremulous motion, in a very remarkable 
manner. These tails all have a little knob at their extremity. 
After a short time, or upon any motion in the fluid, the tails 
break away from the corpuscles, but their singular move- 
ments do not cease when this has happened. Sometimes a 
discoid enlargement forms on some part of the tail, and then 
the tail suddenly retracts itself into a larger granular and 
coloured particle. That the movements of these tails are of 
a peculiar kind, and not due to motion in the liquid, is shown 
by this — that all movement in them ceases entirely when 
they approach near to either of the edges of the covering, 
thin glass. In repeating this experiment, if the surfaces of 
the upper and under glasses come so close together as to 
press upon the blood -corpuscles — which is known by increase 
of their diameter — the tails will not appear. The corpuscles 
must be free from pressure, for the effects described to take 
place. Moreover, tails are not readily produced if the 
stand of the microscope and the glasses are cold; the phe- 
nomenon takes place much sooner, and the tails are longer, 
when the instrument and fluids have been for some time in a 
warm room. 
