rated as occasion required. Once or twice in the course of the proceedings, when the oxygen ventilation was for brief intervals suspended, the effects of carbonic acid became markedly symptomatised by difficulty of respiration, lividity of the nose, and restlessness; these symptoms invariably passed off at once when new oxygen was admitted. At the end of eleven hours the animal became exhausted. The exhaustion was quite different from that produced by carbonic acid. There was no insensibility, no spasmodic breathing, no blueness of the feet or nose, but a general feebleness, and constant turning about, with occasional attempts to recline on the side. As soon as these symptoms were fully developed, I stopped the oxygen, and made the animal completely insensible by narcotic vapour. As soon as insensibility was complete, I removed it from the chamber. It was making eight respirations per minute; the heart-beats being irregular, quick, and feeble. I now, with one or two sweeps of the knife, removed the ribs anteriorily, and laid the heart bare; it was seen pulsating quickly. The right auricle was much distended. The cavities were immediately laid open; a watch-glass full of blood, caught from the superior vena cava, coagulated firmly in two minutes, the clot being intensely red. In the right auricle there was a little fluid blood. In the auricula there was a clot of fibrin, distinctly separated, modeled to the part where it was found, and of about the size of a large hemp-seed. The inner surface of the auricle was coated with a fine layer of fibrin, which was easily removable with the point of the scalpel. In the left cavities, fine web-like cords of fibrin were interlaced with the chordæ tendineæ. To the free margins of the aortic valves there were

firmly attached three semi-transparent beads of fibrin, each of the size of a small pin's head. The aortic valves were fringed, on their free margins, with fibrinous beads, one valve having also a swollen and reddened In the aorta there lay a thin but long

appearance.

thread of fibrin.

The lungs contained some blood, but were not congested. They were, however, firmer in structure, and less elastic than natural. They floated in water. The vessels of the brain were congested. All the other organs were natural in structure, but unnaturally red in colour.

The operation of laying open the heart extended only over one minute; the organ was opened while yet briskly pulsating; and several attempts at respiration were made by the diaphragm and the chest muscles after the fibrinous deposition had been exposed to view.

EXPERIMENT III. Inhalation of Oxygen. By means of the apparatus described in the last experiment, I subjected a pigeon to the influence of oxygen gas. The experiment commenced at 11 a.m. For six hours after the inhalation but little change was observed in the animal; but at this time, the administration of the gas having been suspended for ten or fifteen minutes while the gasholder was being re-supplied, a severe paroxysm of dyspnoea supervened, but disappeared immediately when a new charge of gas was driven through. At 8 p.m. (nine hours after the commencement of the experiment). the creature became feeble, and each inspiration was attended with a peculiar croupy sound. The respirations were now 28 per minute, and the croupy sound, which was so loud that it could be heard through the walls of the chamber, continued well marked for two

hours. There were the same indications of thirst as were noticed in the guinea-pig. The peculiar noise in the breathing subsided gradually, as a sleep supervened which lasted until half-past eleven, and was remarkably natural. On waking up at the hour named, the creature was less embarrassed in the breathing than it had been before, but it was much exhausted and restless. Its feathers were widely expanded out, and at times it reclined partially on one side. The beak, the eyes, and the feet were intensely red in colour, an appearance which commenced about four hours after the inhalation, and which continued to the end. At 12 o'clock, midnight, (i. e. thirteen hours after the inhalation began) I produced rapid narcotisation. As is usual in birds, the effects of the narcotic were at once developed, and in one minute and a half I removed the animal from the chamber perfectly insensible. The inspirations taken before the body was opened were three in the quarter minute, and deep. The chest was now quickly opened, and the heart laid bare. The muscular action on both sides was rapid. The right auricle, on being opened, was found in great part filled with a firm coagulum, modeled to those parts of the heart-wall against which it had rested. The clot was coloured by red matter. From this coagulum a cord ran downwards into the right ventricle, and, taking the course of the circulation, curved thence upwards for a short distance. But the most remarkable appearance was met with in the left ventricle. Here a firmer coagulum took a bulbous origin at the lower part of the cavity; from this there ran upwards a neck, which, as it approached the auriculo-ventricular valve, divided and ran along the borders of the valve, making a circle or ring from

which a prolongation was sent upwards into the aorta. At the point where this prolonged cord crossed the aortic valves, it narrowed evidently from the valves having closed upon it during the time the heart was acting, and above expanded itself so as to fill up a fourth of the diameter of the artery. This concretion, at its lowest or bulbous part, was beautifully moulded to the adjoining muscular wall, and it was so firmly attached to the muscular structure that it could not be removed without risk of breaking it away. It was also firmly attached to the valve. The side sketch gives a perfect representation of this concretion.

A.

B.

Fig. 5.

Aorta, with prolongation of
Cavity of right ventricle.

the concretion traversing it.

In both sides of the heart there was, in addition, some fluid red blood, of the same colour on each side. This, on being removed into a watch-glass, coagulated (at a temperature of 60° Fahr.) in fifty seconds; the clot being very firm, and no serum exuding ultimately from it. The blood corpuscles seemed to have undergone no modifications. The other organs were intensely red: and in the upper and lower parts of the trachea, for the space of half an inch, there were distinct exudations of plastic lymph; in the upper part the exudation blocked up the passage to a considerable extent; thus accounting in full for the noisy inspiration which had been so marked in the course of the experiment.

These experiments, then, definitively settle in the affirmative the question;-Whether coagulation of blood and separation of fibrin may occur in the body during life? The pathological conditions produced in all the animals, may be considered as those of active hyperi

nosis; while in the pigeon the local manifestations rendered the case a very correct imitation of the disease called croup in the human subject.]

Relative Increase of Fibrin. The second class of cases, to which I referred at a previous page (64), are those in which the excess of fibrin is relative only; that is to say, the quantity of fibrin itself is not absolutely above the natural standard, but the serum and some other blood constituents are reduced below their natural figure. The results in such examples are the same, under certain circumstances, as in the last instance; i. e. the fibrin is laid down in a separate form in the circulating organs. This kind of separation not uncommonly occurs upon the setting up of profuse colliquative sweating or purging, as in the latter stages of phthisis pulmonalis, and also in cases of cholera, where a separated clot of fibrin is by no means unfrequent in the right side of the heart, and even in the aorta, albeit the remainder of the blood is in a semi-coagulated condition. In one case of phthisis pulmonalis, ending rapidly from diarrhoea, I found both sides of the heart filled completely with firm fibrinous coagula, which, when weighed after removal, were found to exceed 200 grains. The remainder of the blood was also firmly coagulated. The lungs were less changed in structure than is usual in fatal cases of phthisis; the characteristic signs of the disease being confined mainly to the apex of the left lung. The rapidity of the fatal event had, indeed, resulted more from the profuse elimination from the skin and the bowels, and the consequent formation of the concretions, than from the failure of the respiration.

Deposition from Obstruction. In the third place, I infer, from numerous observations, that the deposition