ON THE COAGULATION OF THE BLOOD 107 
sufficient quantity to overcome the feeble alkalinity of the blood, while the 
acidulated specimen retained the property of coagulating very rapidly when 
raised in temperature. But on attempting to discover whether this blood was 
really acid in reaction, I found that its red colour entirely vitiated the indications 
of both litmus and turmeric; and even the serum obtained after contraction 
of the clot was too much tinged to admit of the satisfactory application of the 
test-paper. 
| Being thus baffled in my experiments with the sheep, I had recourse to the 
horse, in which the red corpuscles subside with peculiar rapidity in the plasma, 
giving rise to the buffy coat well known to occur in the blood of that animal 
in the state of health, so that the opportunity would be presented of obtaining 
liquor sanguinis free from red corpuscles, to which the tests could be applied 
without risk of fallacy. Accordingly, yesterday afternoon, a horse having been 
placed at my disposal by my friend Mr. Gamgee of the New Veterinary College, 
I tied into the right jugular vein one end of a piece of vulcanized india-rubber 
tube, four yards in length, the greater part of which was coiled up in a freezing 
mixture, and some of the blood, having been allowed to remain for a while in 
the tube, was shed into vessels standing in ice-cold water. Its temperature 
on first escaping into the air was 39$° Fahr., and having been since kept in 
the cold it is still only partially coagulated at the present time (twenty-nine 
hours after it was shed). At first, however, it appeared as if we were likely 
to fail, the blood of this horse being a rare exception to the general rule, in 
exhibiting for a long time no appearance of the ‘sizy’ layer. But after it had 
stood for about two hours, I succeeded in removing from the surface, by means 
of a glass tube, a sufficient amount of liquor sanguinis for the performance of 
an experiment, taking care that the glass into which it was shed, and the tube, 
were both near the freezing-point. To half a drachm of this plasma I now 
added one minim and a half of moderately dilute acetic acid, which had the 
effect of rendering it distinctly acid, as indicated by its communicating a red 
tint to litmus and restoring the colour of turmeric paper which had been 
reddened by dipping it in the portion of the hquor sanguinis which had not been 
acidulated. I kept the specimen in ice-cold water till this evening. For a long 
time it remained perfectly fluid, except the formation of little soft coagulum 
at the surface, just as in the unacidulated blood; but a few drops placed in 
a watch-glass and brought into a warmer atmosphere, coagulated in about the 
same time as the blood that first flowed from the tube, a soft clot forming in 
about a quarter of an hour. Even at the expiration of twenty-four hours a 
portion of what remained in the cold was still fluid, though faintly acid, but 
set into a pretty firm clot on being removed into a warmer situation. 
