on the main air-passage. 2. Dislocation of the vertebræ. 3. Arrest of the circulation in the brain, from compression of the vessels of the neck.

In the first two modes, the death is almost immediate, and the blood is ordinarily fluid. In the last named mode, life may be long sustained with comatose symptoms; and the blood, after death, may be found not only coagulated, but with distinct deposition of fibrin, laid down during life, and leading to the fatal termination.

The following example is in point.

On Wednesday, 30th November, 1853, I was called to a man who had attempted suicide by hanging. He was tall, and the beam to which he had suspended himself was low, so that his feet touched the ground, while his shoulder rested against a wall. He had on his neck a stiff stock, and the cord rested anteriorly on this, but laterally pressed on the neck. He was hanging several minutes before he could be cut down, as the door of the room was secured within. When he was relieved, his face was congested, and he was profoundly insensible, but soon commenced to breathe, and when I arrived he was breathing well. I had him laid in bed, and bled him freely; once from the arm, and once from the temporal artery. The blood flowed readily, and the arterial blood was of bright red colour. The bleeding had no effect. The man reclined like one in catalepsy. He was quite unconscious; and wherever his limbs. were placed, there they remained. After a lapse of eight hours, the temperature of the whole body, the head and face excepted, became greatly raised; the pulse got hard; and all the acute general symptoms of an inflammatory fever were manifested. Through the

succeeding twenty-four hours he remained in this state, having no power to swallow. The dry heat was followed by profuse perspirations, which bathed the whole body, except the head and face; these remained cold as marble. Through the succeeding twenty-four hours he continued much the same; the pulse 120, and hard; the breathing forty per minute; the skin hot, with occasional free perspirations. On the third day, the heart began to intermit, and the symptoms of obstruction on the right side of the heart from concretion, such as I have described, were so obvious, that both Dr. Willis and myself predicted the existence of fibrinous deposition and its results. Never becoming in the least conscious, the man gradually sank, and died late in the night of December 2nd, the respiration outliving the heart's action.

At the post mortem examination, which Dr. Cormack and Dr. Willis attended, we found that the main airpassage had altogether escaped injury or compression, and that the first symptoms were purely due to extensive congestion of the brain. The brain was found intensely vascular, with free exudation of serum beneath the arachnoid. The lungs were somewhat congested. The right side of the heart was distended to an incredible size with firmly coagulated blood, on the upper surface of which lay a fibrinous layer. Attached to the wall of the ventricle, at the commencement of the infundibulum, was the base of a large fibrinous tube, which ran upwards into the pulmonary artery, and extended into its branches. The deposit was laid down in distinct strata, and formed a perfect hollow cylinder, containing in its central axis a column of red blood. There was no trace of active disease in any

other organ, but some congestion of the liver, spleen, and kidneys.

In death from the excessive imbibition of water into the circulatory system, the fluidity of the blood is sustained; while, after death by the electric shock, there is not merely fluidity of blood, but, as it would seem, general disintegration.

In instances of slow poisoning, as by the alkalies or antimony, where the blood is found fluid, and the corpuscles more or less disintegrated, there is found also extensive congestion of the soft tissues. This condition must be scrupulously disconnected from all idea of inflammation or its upshot. The congestion has two sources. First, the blood being abnormally fluid, easily flows, as Plato has it, "through the thin structures." Secondly, when the more solid parts of the blood, as the fibrin and blood-corpuscles, undergo extensive liquefaction, the volume of the mass of blood augments and exerts a passive pressure from within upon the vessels, in addition to the active forces pertaining to the normal circulation.

After death from starvation, the blood is semicoagulated (see case, page 126). This rule is not strictly absolute; for in a late instance of death from stricture of the oesophagus, in which the patient swallowed no solid food and but little fluid, for the long period of twenty-three weeks, and in which death arose from pure inanition, I found the blood, both on the right and the left sides of the heart, separated into a thick fluid part and a distinct fibrinous layer.

Fluidity of blood in the sinuses of the skull of the adult, is rather a normal than an abnormal indication; for, in the closed cavity of the skull, if there be no

breaking down of the brain-substance, the blood remains fluid much longer than in the other parts, even after hæmorrhagic death.

Foetal blood, according to my observations, is always either fluid or but semi-coagulated. Even if the fœtus be healthy, the force of coagulation is low; if the fœtus be the victim of syphilis, the blood is uncoagulable, and the corpuscles are misshapen and easily soluble. A very few independent respirations, however, on the part of a healthy new-born child, give to the blood plasticity and firm coagulating power. Hence firm coagu

lation of blood may be added as an accessory sign that a child has breathed.

In a placenta, however, which has undergone softening or destruction of tissue, blood may be effused, and coagulate in which case the foetus dies, as from syncope. Hence, in cases where a foetus, apparently healthy, is born dead without any obvious disease, the condition of the placenta should be carefully observed.

In cases of sudden death in women, after or before parturition, it is important always to examine the pulmonary artery and aorta for fibrinous deposits.

In all cases of mysterious sudden death, where the cause is not at once obvious on dissection, the pulmonary artery ought to be carefully examined; and this observation ought not to be confined to the main trunk, but extend to its ramifications.

If, in making a post mortem examination, in which the reason of sudden death is obscure, the right as well as the left sides of the heart are found full of blood, the inference is fair and almost demonstrative, that the death was not due to arrest of the circulation in the lungs, but to death commencing at the heart-syncope. If, on the

other hand, the right side of the heart is distended with blood, and the left side is found quite empty, the inference is fair and almost demonstrable, that the arrest of the circulation commenced in the pulmonic circuit-apnoea. There are indeed, according to strict rule, only two real causes of death; death commencing at the heart-syncope; and death commencing at the lungs-apnoea; though these two modes admit of combination. Other so-called modes of death, coma and asthenia, are but forerunners, or, as it were, preceding diseases. If the heart and circulation continue in play, together with the respiration, there can be no death. This is a truism; but it is necessary to state it, that the forms of death may be reduced to their proper number in a physiological point of view. A man may lie comatose for hours, or even weeks, but he need not therefore of necessity die; nor does he, thus lying, begin to die until such time as his circulation or respiration begin, one or other, or both, to fail.

Much has been said and written about the differential diagnosis of the blood of man and of other mammalia. For my own part, I am free to say that, if specimens of blood from man, from the sheep, ox, pig, guinea-pig, dog, cat, or rabbit, were placed before me, I should be utterly unable to say with precision, from any examination which I could institute, chemical or microscopical, from which of these animals the different specimens were derived. The size, and to some extent the shape, of the blood-corpuscles, are not, indeed, alike in the same individual or in the same animal at all times. A mere difference in the specific gravity of the blood is alone sufficient to cause modifications of the corpuscles.