rhagic diathesis, which does not pertain to uræmia; there are the outward manifestations of this diathesis in petechial eruptions, and fluxes of blood, none of which are presented in uræmia; while there is little evidence of prolonged coma, which symptom is the leading symptom of uræmia.

But while a distinction may clearly be drawn between the symptoms of uræmic toxæmia and of ammoniacal toxæmia, I must confess that the fatal shaft driven home from either bow leaves pathological consequences, which it would be hard to separate. Requesting the reader (if to this question his interest in it will be the leader of his industry), first to recast the pathological changes, which have already been described as incident to uræmia, I would ask him next to follow out in comparison the following history of the pathological condition, presented by the animal described at pages 184-87, after its subjection to the effects of carbonate of ammonia to a fatal termination.

The body of the animal, sent to me for examination, was inspected about thirty hours after death. The structures were still quite fresh. There was slight cadaveric rigidity. On reflecting back the chest-muscles, they were found remarkably dark in colour, an appearance which extended through the whole muscular system, and indeed through all the soft parts. The muscles were soft in structure, and easily torn. Fluid blood exuded from the divided parts. The lungs, the liver, and the kidneys were dark, and intensely congested with fluid blood. The

liver and kidneys were soft in structure, and blood exuded from incisions made into them. The bladder was charged with urine, which evolved ammonia freely, and which, subjected to heat and nitric acid, was found to be highly albuminous. The specific gravity of the urine was 1035. The brain was congested with dark fluid blood. The stomach was vascular on its inner surface. Along the alimentary canal, vascular spots were here and there met with. There was no effusion into any of the serous cavities. The lungs were congested, and the bronchial mucous membrane was injected in points, but everywhere lined with secretion. The heart was filled with blood on both sides. The blood was entirely fluid; and evolved ammonia so freely, that by holding over it, at a slight distance, a surface of glass moistened with a little dilute hydrochloric acid, the glass, on drying, was frosted with crystals of chloride of ammonium. The blood on both sides of the heart was dark in colour. Each variety was exposed to the air in a small evaporating cup, at a temperature of 65° Fahr. Thus exposed, the specimens continued fluid for thirty hours, and then commenced to coagulate, eventually coagulating so far as to become modelled to the containing cup, and to admit of being turned out of it as a shaped mass. There was, however, The blood-corpuscles presented the same modification as were observed during life. They were stellate, many-sided, or collapsed; none were perfect.

no separation of serum.

From the morbid appearances, then, presented after

death, both by uræmia and by ammonia, we might be induced, if we rested on them alone, to base a suspicion that Frerichs' view is correct. But on further inquiry we are led to put aside even this reading of the phenomena observed. For the fact stands out that the morbid appearances from uræmia, so analogous to those produced by ammonia, are probably dependent on changes occurring late in the act of life, and, to a certain extent, on decompositions occurring after life itself has ceased. We are consequently driven back upon the symptoms as the indices from which to read off the effects of the two poisons, and are enforced to allow the post mortem signs to remain in each case as the results of changes induced by poisons, which in character closely approach each other, which in their final effects, when they destroy life, leave behind similar imprints, but which exhibit in the course of their action certain specific differences, dependent on the physical differences of the poisons themselves.

One other point only relating to the respective effects of urea and carbonate of ammonia, in relation to uræmic coma, at present occurs to me as requiring special attention. I have already shown that carbonate of ammonia, acting as a poison on an animal body, produces a condition of blood in which the dissolution of the fibrine is so marked, and the disintegration of the blood-corpuscles is so marked, that hæmatine is set free, the fluidified blood is exuded as blood, and a hæmorrhagic condition is elicited. I have shown again that in uræmia this condition is not set up, but that such effusions as are produced

are simply serous in character. This very marked distinction led me to test the relative effects of carbonate of ammonia and of urea on blood recently drawn; the following short record of the experiences thus obtained includes the facts of this inquiry.

Mixed blood drawn from the neck of an ox was used for the experiment: the natural period of coagulation of two thousand grains of this blood was six minutes.

Two thousand grains of the blood was received into a cup containing four grains of ammonia in one fluiddrachm of water. The blood thus treated, when left at rest, remained permanently fluid, and of port wine consistency. On agitation, fibrine could not be whipped out; nevertheless, on addition of caustic baryta at 60°, a portion of this blood readily coagulated with free evolution of ammonia. Examined microscopically, the corpuscles were found almost entirely dissolved.

At the same time, and from the same animal, two thousand grains of blood were received into a bottle containing four grains of urea in one fluid-drachm of water: this blood coagulated in nine minutes. The clot was unusually dark and jelly-like; the corpuscles underwent very little change, until decomposition commenced.

At the same time, two thousand grains more of the blood were drawn into a cup containing eight grains of urea in a fluid-drachm of water. This blood coagulated within a few seconds of nine minutes; it formed also a dark softish clot, and its corpuscles

underwent no peculiar modification prior to putrefaction.

Into another cup there were received two thousand grains of blood; this cup contained sixteen grains of urea, in solution with one drachm of water. The blood coagulated a few seconds earlier than the specimen which was left to coagulate normally; its corpuscles underwent no modification, and the clot formed, though very dark, was moderately firm.

Lastly, two thousand grains of blood from the same animal were caught in a cup containing thirtytwo grains of urea dissolved in a drachm of water. Coagulation occurred in five minutes, the clot being dark but firm, and yielding an abundance of serum. The corpuscles were unaltered so long as the mass remained free from putrefaction.

Thus, in respect to the physical effects of urea on blood, we learn the curious fact, that the salt in its concentrate form has no power to hold the blood fluid; but that reduced or diluted it does hold the blood temporarily fluid, although not to the same extent of fluidity as is so often met with in uræmia. This truth elicited, it was necessary to determine the effects of more dilute solutions of urea on blood. For this purpose I selected the blood of sheep, because the effects are more rapidly determined, and the influence of solvent bodies are more thoroughly brought out the results are herewith given.

Into a cup capable of holding 2000 grains, four grains of urea were placed, dissolved in four fluiddrachms of distilled water. Into this cup were re