424 Proceedings of Boyal Society of Edinhurgli. [july 2, 
present Session an account of their experiments with mammalian 
blood. These have been printed in its Proceedings and in the 
Journal of Anatomy and Physiology. 
They demonstrated tbat human blood received into castor oil 
from the finger-tip remains perfectly fluid so long as it is kept from 
contact with any solid matter. Under these conditions, the white 
corpuscles remain perfectly round, and the blood-plates retain the 
appearances they present in the living blood-vessels. It is contact 
with solid matter that causes these blood elements to become sticky 
and to change their shape. Solid matter may therefore be looked 
upon as a mechanical stimulus to the corpuscles. 
Two things result from the action of the solid, viz., the formation 
of fibrin, and a change in the morphological characters of the white 
corpuscles and of the blood-plates. 
Fibrin has been looked upon as the result of a breaking down of 
corpuscles. 
We are of opinion that it is produced by the corpuscles whilst 
still in a living condition. The production of fibrin may be looked 
upon, therefore, as the result of a metabolism induced in the cells 
by mechanical stimulation. We fail to observe by means of im- 
proved methods, already detailed in that paper, any evidence of the 
breaking down of corpuscles during coagulation ; although of course 
the corpuscles of blood-clots must die and break down eventually., 
owing to the absence of a suitable environment. Many, however, 
remain alive for days, as seen in the clots which we experi- 
mented on. 
In invertebrate blood the clot is formed, at any rate for the 
greater part, by the welding together of blood-corpuscles. These 
throw out processes which interlace to form a solid mass. It was 
to be expected that, if solid matter acts as a stimulus to the white 
mammalian corpuscle, and that such a stimulus is required to 
induce it to change its shape, as in our experiments it seemed 
to do, the invertebrate blood would remain fluid if prevented from 
coming in contact with solid matter, as by receiving it into castor 
oil. In the absence of mechanical stimuli the corpuscles would 
not change their shape, and consequently no plasmodium would 
be produced. 
Blood was obtained from a crab, previously anaesthetised, by 
