Seven or eight cubic inches of common air were injected gradually into the crural artery of a large dog. A peculiar rustling noise, depending upon the admixture of the air with the blood, accompanied the operation. No particular symptoms followed; but after some minutes the corresponding vein became distended with frothy blood, which moved with difficulty, and became stagnant in the vessel. The whole limb crepitated upon pressure, but no untoward symptom presented itself for more than half an hour. An ounce of water, to which seventy drops of medicinal prussic acid had been added, was now injected into the same artery. This produced no apparent effect upon the constitution.
A quarter of an hour after, an ounce of saturated solution of nux vomica was injected into the same vessel. This also was followed by no particular symptoms. An hour after the first injection, half an ounce of a weak infusion of tobacco was introduced into the same artery. Excessive pain immediately followed, accompanied by great rapidity of breathing. The animal now appeared as if he were going to die; however, he slowly recovered, appeared giddy and inclined to vomit, and kept himself in a continual state of restlessness. This condition was succeeded by fever, accompanied by extreme sensibility of the limb, and irregularity of the pulse. At the expiration of some hours, he appeared better; the pulse became more regular and less feverish, but the leg continued swollen, and extremely painful upon pressure. During the night, the pain returned, indicated by howling and restlessness. There were several evacuations of fæces and urine. The following morning, there was great prostration with much fever, and apparent suffering. The limb was slightly emphysematous, swollen, inflamed, and infiltrated with serum.
On the following day, two ounces and a half of water, in which some nux vomica had been boiled, were injected into the crural artery of the opposite limb. The dog expressed no pain; but, at the expiration of ten or twelve minutes, slight convulsive motions became evident, which were gradually converted into violent tetanic spasms. The animal threw himself backwards with his limbs extended, and died, after repeated convulsive attacks, an hour and a half after the last injection.
Post-mortem appearances. On opening the body, no unusual appearances were observed in the limb upon which the last experiment had been tried, but the opposite one was tumid and emphysematous, infiltrated with a greyish red frothy serum of a fetid odour. The small vessels were obstructed by firm clots of blood. The gall-bladder was greatly distended; and the intestinal canal contained a quantity of yellowish mucus.
PART II.
ON THE INTRODUCTION OF VITIATED FLUIDS INTO THE BLOOD; ITS CONSEQUENCES, AND TREATMENT, WITH CASES.
VIII. The experiments cited in the first part of this essay, illustrate the power possessed by the blood of preventing certain foreign substances from circulating with it. They shew that pus, in particular, has a tendency to coagulate the blood; and that by this means, when introduced into the vessels, its progress is arrested in some part of the circulating system. This fact, which, taken by itself, might appear of little consequence, assumes considerable importance when considered as one of the inherent properties of the blood, at all times ready, under favourable circumstances, to be called into action in the living body. The conditions under which pus will determine the coagulation of the blood, and those under which it will circulate in the living vessels, require to be accurately ascertained, before we can rightly interpret the discordant evidence which we at present have upon this point.
Dr. Sédillot,[29] in a work recently published, mentions, that a great number of cases are met with, in which pus is poured into the general circulation without meeting with any obstruction, and states that, in such instances, he can detect the globules of pus in different parts of the circulating system. He even affirms that he can recognise a disease caused by purulent infection, by examining, under a microscope, a portion of the blood abstracted from the body.