4 
Observations on "Granulated'^ Blood-discs. 
By George F. Pollock, Esq. 
(Read June 29th, 1859.) 
When a drop of blood, taken from any part of the human 
body, is examined by the microscope with a suitable power, 
say from 300 to 600 diameters, every observer is aware that 
- — besides the ordinary red discs of a flattened form, having a 
depression in the centre on both sides, with a circular and 
perfectly even outline — there are others of which the exterior 
surface is quite irregular. Some appear flat, with a crenated 
border. Some, approaching more or less to a spherical form, 
are covered with little tubercles, giving them a granulated or 
mulberry-like appearance. That these irregular discs are all 
formed from the circular ones can admit of no doubt. Indeed 
they have often been called degenerated blood-discs, and the 
change, as it takes place out of the body, may be observed 
under the microscope. The most convenient way of doing 
this, is to put a little oil or varnish round the edge of the 
thin glass cover under which the drop of blood is placed, 
which, by preventing its drying up, enables the examination 
to be continued for some time. In some discs the change 
takes place rapidly in the course of a few minutes, in others 
it never takes place at all, and the only change to be seen 
after the interval of a day or two is that they are smaller in 
size and less flattened in shape. The first change in a circular 
disc which is about to become granulated, consists in the 
appearance of spots where the ^terior membrane seems 
thinner and more transparent than elsewhere, and it is at 
these spots that the granules or tubercles make their 
appearance. It would seem that these spots are caused more 
by a contraction of the intervening thicker portion of the 
membrane than by an expansion of the thinner portion, for 
the diminution in size, which is observed in all the discs after 
the lapse of some hours, takes place much more rapidly and 
to a greater degree in the granulated discs than in the others. 
Together with the appearance of these spots the disc 
usually assumes a less flattened and more rounded shape. 
The granules are usually most numerous at the edge of the 
disc, where they are first observable, giving it a crenated 
appearance. Gradually, as they increase in size, the outline 
becomes sharper, till they sometimes present an almost spiked 
appearance. This change will be gone through in a period 
