6 Pollock, on " Gramdated" Blood-discs. 
described^ the final stage of the process, that is, the breaking- 
up of the individual discs — owing to the motion of the blood 
in circulation — might well be supposed to be more rapid and 
more complete ; and this would account for the presence in 
blood of the minute particles before mentioned, which might 
then be regarded as the debris of previously existing discs. 
I have not, however, been able hitherto to detect any such 
alteration in the form of the discs while in actual circulation 
in the living body. 
Having often seen changes of the same nature, though 
not quite similar in appearance, take place in the discs of 
blood taken from frogs and newts, I first tried carefully if 
I could discover any granulated discs in the blood while in 
actual circulation in the web of a frog's foot, examined in the 
ordinary way. I next tried the gills of the tadpole of the 
great water-newt {Triton cristatus), which, from their greater 
transparency, permit the individual blood-discs to be better 
seen. In neither instance could I perceive any granulated 
discs, though in both cases discs of an unusual form some- 
times occurred. I next examined the blood while circulating 
in the arteries and veins of the mesentery in kittens and 
rabbits, while under the influence of chloroform, having, in 
most cases, previously examined the blood obtained by 
pricking the skin of the animal, and found an abundance of 
granulated discs. The membrane of the mesentery is so thin 
as to afibrd the fullest opportunity of examining the individual 
discs, when the circulation is sufficiently slow, but I have 
never been able to detect granulated discs while the animal 
has remained alive, though I have often seen an abundance 
of the small particles before described in rapid circulation. 
Almost immediately after the death of the animal, many of 
the discs begin to assume the granulated appearance, whilst 
others remain unchanged. Whatever be the cause of this 
difference (which may, perhaps, depend upon the age of the 
discs, the younger ones resisting the change), exposure to the 
air does not seem to have anything to do with it, for whether 
the effect of the air is, or is not, sensible through the very 
thin membrane of the mesentery, the discs in the smaller 
vessels are all equally exposed to that effect. I make this 
remark because, from the granulated discs being always found 
to be most numerous at the exterior edge when a drop of 
blood is covered with thin glass, some difiference might be 
supposed to result from the outer ones being the most ex- 
posed to the air. This position of the granulated discs may, 
however, easily be shown to depend on mechanical causes ; for 
if a piece of thin glass be raised at one end the thickness of 
Hr 
