Pollock, on " Granulated" Blood-discs. 
7 
a hair, by means of a drop of dried varnish placed under the 
two corners at one end, and d drop of blood be then allowed 
to run underneath from the raised end, the irregular discs 
will at once be all found at the other end ; they are smaller 
in size, usually free and detached; they present a rougher 
and more extended exterior surface, and they appear to be 
slightly inferior in specific gravity; when, therefore, what 
may be called a capillary rush of the fluid takes place, as it 
always does when a drop of blood is covered with thin glass^ 
the granulated discs are naturally carried to the greatest 
distance. Again, there is no difficulty in obtaining dried 
blood free from granulated discs, which could hardly be the 
case if the change were occasioned by exposure to the air. If 
it be so, that no such changes as these ever take place while 
the blood is alive in circulation, the inquiry becomes com- 
paratively uninteresting, though, even then, it may tend to 
throw light upon what is the ultimate structure of the discs ; 
but having regard to the very different degree in which, after 
death, some of the discs evince a tendency to undergo the 
change as compared with others, while some resist it 
altogether ; it would seem highly probable that there must 
be a corresponding difference of condition or structure during 
life, though, for the present, we may be unable to detect it. 
My opportunities have not enabled me to make comparison 
of the blood obtained from persons suffering under different 
forms of disease ; but having examined it in persons of all 
ages and both sexes, obtained when the stomach has been 
full and when empty, after fatigue and after rest, and at all 
hours of the day, commonly by pricking the finger, but 
frequently from deeper incisions, and, in the case of rabbits 
and cats, obtained from various parts of the body, especially 
from the larger arteries and veins, I have never found an 
instance in which a drop of blood, placed under thin glass the 
instant it was drawn, and examined in the usual way, did not 
at once exhibit granulated discs in greater or less abundance, 
if not elsewhere, at all events at the exterior edge of the 
drop. 
In conclusion, I need hardly say that the preceding ob- 
servations are in no degree applicable to the white or colourless 
discs. 
