194 ON THE COAGULATION OF THE BLOOD 
seen in any amputated limb in which the blood-vessels are sound. If such a limb 
is examined, say twenty-four hours after amputation, you will find that there 
exist clots in the vessels where they were wounded by the knife in the operation, 
but that elsewhere the blood remains fluid and coagulable. I came, therefore, 
to the conclusion that an undisturbed blood-clot is unable to induce coagulation 
in its vicinity ; and I think that the instances I have given demonstrate that such 
is really the case. 
Yet in the experiment which I have described, where a glass tube was slipped 
down into the jugular vein, the coagulum did propagate itself. I found, as 
before mentioned, on examining such a tube ten hours after it had been charged 
with blood, that the crust of clot which lined the tube was only a thin one ;_ but 
in another experiment, nearly two days having been allowed to pass before 
examination, the layer of clot was thick, and there remained only a small channel 
in the middle of it, with the blood still fluid and coagulable. How is this dif- 
ference of behaviour between the clot within the vessels and the clot outside them 
to be explained ? At the time when I performed the experiment, I was disposed 
to think that it must be due to some imperfection in the mode of performing 
it; that in spite of all the care that I had taken in very steadily pressing down 
the very thin glass tube, nevertheless the blood must have been influenced by 
the glass for some considerable distance. 
Iam now inclined to believe that another explanation must be given. It 
was ascertained by Schmidt that (to adopt provisionally his original nomen- 
clature) the fibrinoplastic substance emitted by the corpuscles is in excess of 
what is required in order to combine with the fibrinogen of the liquor sanguinis. 
This, in fact, is obvious from the fundamental truth that serum expressed from 
a shrinking clot, when added to hydrocele fluid, induces coagulation. The blood 
is coagulated already ; the fibrine is already formed in it; and yet the serum 
contains fibrinoplastic substance in solution free to combine with the fibrinogen 
of the hydrocele fluid. Such being the case, we see that, in the experiment with 
the glass tube, the clot first formed under the influence of the glass, shrinking 
and squeezing out its serum containing fibrinoplastic substance, this must com- 
bine with the fibrinogen of the adjacent liquor sanguinis, forming fresh fibrine, 
and producing a new layer of coagulum. 
This, however, will only account for a very limited extension of the clot ; 
inasmuch as the fibrinoplastic substance of the original coagulum having now 
all completely combined with fibrinogen, none will remain in solution, and thus 
the serum pressed out by the shrinking of the new layer will not contain fibrino- 
plastic substance, unless some new agency comes into play, to induce the cor- 
puscles of the last-formed coagulum to give it up. Such an agency is, I suspect, 
