Motion, and next Morning it was dead and much
swelled.
“ In Presence of, and assisted by Mr. Robert
Fullarton, a curious Gentleman, and very dextrous
in Microscopical Observations (in August 1733) I
conveyed through a Small Glass Tube a few Drops
of a Solution of Opium in Water into a Frog’s
Stomach, and putting the Animal into a Glass
Cylinder, adapted it so to a good Microscope, that
we had a distinct view of a part of the Membrane
betwixt the Toes of its hinder Foot, where the
Circulation of the Blood may easily be seen. My
Design was, since I found Opium killed frogs, to
observe if there was any visible Change made by it
in the Blood itself, or in its Motion ; neither of us
could indeed see any Alteration of the Blood as to
its Consistence, Colour of the Serum, Magnitude,
Figure or Colour of the red Globules ; hut we very
distinctly saw a surprising Diminution of the
Blood’s Velocity, for it did not move half so
swiftly as it use to do in these Creatures. We
alternately looked at it again and again, and in less
than half an Hour saw the Velocity of the Blood
gradually increase, the uneasy Frog recovered its
wonted Vigour, and the Blood its common celerity
; upon which we took out the Paddock,
put it in a bason of clean water, and allowed it
half an hour to refresh itself, then gave it another
Dose of Opium, fixed it to the Microscope with
all expedition, and viewed it as before ; the blood
then moved yet slower than it did the first time;
and, its Velocity gradually decreasing, at length
it stagnated, first in the smaller, then in the
larger vessels, and in about a quarter of an Hour
the Animal expired. One thing was very observable
all along, viz. That notwithstanding the
diminished Velocity of the Blood, there was no
sensible Diminution of the Frequency of the Pulse ;
yea, when there was no Circulation or progressive
Motion of the Blood in this part, the Pulse was
visible by an undulating Motion ; that is, the
Blood returned as far back at every Diastole of
the Heart, as it was protruded by the preceding
Systole ; this continued till the Frog was quite
dead, or at least appeared to he so. When we
had lost all Hope of its Recovery, I open’d it,
and found nothing in its Stomach but a clear
Mucus like a Geliy, a little coloured with the
Opium, of which it was full ; every thing else
seemed perfectly natural. This Experiment we