ON UTE COAGULATION OF THE BLOOD 125 
process would not take place had not the blood been prepared for the change 
by contact, during the process of shedding, with the injured orifice of the blood- 
vessel and with the surface of the receptacle. I have only very recently become 
acquainted with the remarkable subtlety of the influence exerted upon blood 
by ordinary solids. I was long since struck with the fact that if I introduced 
the point of an ordinary sewing needle through the wall of a vein in a sheep’s 
foot and left it for twelve hours undisturbed, the clot was still confined to a 
crust round the point of the needle, implying that coagulum has only a very 
limited power of extension. I thought, therefore, that by proper management 
it might be possible to keep blood fluid in a vessel of ordinary solid matter 
lined with clot. But various attempts made with this object failed entirely, 
till I lately adopted the following expedient. Having opened the distal end 
of an ox’s jugular vein containing blood and held in the vertical position, taking 
care to avoid contact of any of the blood with the wounded edge of the vessel, 
I slipped steadily down into it a cylindrical tube of thin glass, somewhat smaller 
in diameter than the vein, open at both ends, and with the lower edge ground 
smooth in order that it might pass readily over the lining membrane, and so 
disturb the blood as little as possible by its introduction, and influence only 
the circumferential parts of its contents. The tube was then kept pressed 
down vertically upon the bottom of the vein by a weight, in a room as free as 
possible from vibration, and I found on examining it at the end of twelve hours 
that the clot was a tubular one, consisting of a crust about one-eighth of an inch 
thick next the glass and the part exposed to the air, but containing in its interior 
fluid and rapidly coagulable blood. In another such experiment, continued for 
twenty-four hours, though the crust of clot was thicker, the central part still 
furnished coagulable blood. 
But it may perhaps be argued by those who say that the blood-vessels are 
active in maintaining fluidity that the small portion of the vein covering the 
end of the tube was acting upon the blood, which certainly was fluid where in 
contact with it, the clot being in the form of a tube open at the lower end. To 
guard against such an objection I made the following experiment :—I extended 
a tube like that above described by means of thin sheet gutta-percha, G (Fig. 6 a), 
contriving that the internal surface of the gutta-percha should be pertectly 
continuous with that of the glass tube as represented in section in Fig. 6 0. 
The lower part of the gutta-percha tissue was strengthened by a ring of soft 
flexible wire such as is used by veterinary surgeons for sutures, and the wire, W, 
was also extended upwards to the top of the glass so as to maintain the rigidity of 
the gutta-percha portion during its introduction into a vein, but at the same time, 
from its softness, permit the gutta-percha part to be bent at a right angle after 
