composition of the buffy coat and of fibrin; such as, that the fibrinous coat is nothing more than a modification of albumen, and that the cause of the lighter specific of the fibrinous coat is due to the presence of fat cells and water; but on these particulars it is unnecessary specially to dwell.

Returning to the cause of this peculiar separation of the fibrin coat and its mode of formation, it is to be remarked, that as many hypotheses have been advanced on this subject, as on the composition of the coat itself. Hunter was of opinion that the blood in an inflammatory condition has a greater tendency to divide into its component parts; and that as this blood coagulates more slowly, the red corpuscles have time to subside, and the coagulable part is therefore left free at the top of the fluid. Hewson and others have attributed the separation of the fibrin to its lower specific gravity and its excess. Henle and Nasse state that the time in which the blood corpuscles sink bears an inverse ratio to the time in which the fibrin coagulates. They found that they could produce an artificial buffy coat in ordinary blood by retarding coagulation. Müller pointed out also that if, to a little recently drawn blood, a strong solution of carbonate of potash be added, the coagulation is retarded, the corpuscles have time to sink, and the clot is colourless at its upper part; while Dr. Babington discovered that by receiving blood under oil he could bring about the same result, viz., a buffy coat.

Our countryman, Mr. Wharton Jones, who may be ranked as one of the first and ablest in observing the process of coagulation systematically by the microscope, believes that in buffy blood there is, with a diminution in the quantity of the red corpuscles, an exaltation of

their natural disposition to run into rolls; and that these, again, forming a spongework, squeeze out by their closer aggregation the liquor sanguinis, and by their greater specific gravity rapidly subside. Upon this the liquor sanguinis, which is in such cases proportionally in greater quantities, collects at the top, and the fibrin, coagulating, forms the buffy coat. The opinion, as to the increased attraction of the red corpuscles for each other in inflammatory blood, was pointed out by Mr. Hunter; and even the mottled appearance of buffed blood was described and explained by this physiologist, as attributable to the red corpuscles attracting each other, and forming spots of red. (Hunter's Works, vol. i, p. 235.) Zimmermann concludes that the appearance of the buffy coat is owing to slow coagulation; and that this slowness is brought about by three causes: 1. By an increase of fibrin: 2. By the diminution of the blood corpuscles and their tendency to adhere to each other: 3. By some peculiar properties of the fibrin itself. The blood vesicles, he adds, act as points of crystallisation, just as a straw thrown into freezing water accelerates the formation of ice. He further maintains, that, in coagulated healthy blood, the lowest portion of the clot is the heaviest, the proportion of fibrin in healthy clots being, as proved by experiment, 27 in the lower part, and 73 in the upper; while in inflammatory blood from a pneumonic patient, it was as 3-3 in the lower portion, and 14.8 in the is thus, he says, in inflammatory blood an increase of fibrin, a tendency on the part of the corpuscles to sink, and on the part of the fibrin to rise; hence the result.

upper.

There

In these narrations are embodied the more important speculations with regard to the formation of the buffy

coat. In reference to the modifications arising from the mode of bleeding, the vessel in which the blood is received, and so on, the same remarks apply as were made when treating on the coagulation of healthy blood. One observation more is alone required: viz., that the mere agitation of hyperinotic or sizy blood will tend very much, by hastening coagulation, to prevent the formation of the buffy coat. This fact is described by Sydenham in an interesting passage, in which, after describing the blood as drawn in pleurisy, and the white or tough skin of sanguineous fibres which rises upon pleuritic blood if the current flow freely, he adds:

'Quinimo cùm hoc ipso modo extrahitur, si orificium angustius, sive quid aliud, obstiterit, quò minus pleniori exeat gurgite, neque hic sanguis pleuriticornm sanguinem colore æmulatur, neque æger par exinde commodum capit. Observavi etiam, quòd, si sanguis recens extractus, quocunque demùm modo fluxerit, immisso digito agitetur, superficie rubenti ac floridâ, ut in aliis morbis quibuslibet, spectabitur." (Observationes Medica, sect. vi, cap. 3.)

STATE OF THE BLOOD IN THE BODY AFTER DEATH.

Regarding the condition of the blood in the body after death from various diseases, many important facts have from time to time been observed. Some of the German writers have recently endeavoured to shadow forth a kind of system, or set of fixed principles, on this important point. It would divert me from my present purpose to dwell on this subject; I therefore shall only refer to a few general observations which have at various times been made.

In the first place, it has been argued by Hunter and

D

other observers, that in death from shock, lightning stroke, electricity, and coup de soleil, the blood remains. fluid after death; as also in cases where the fatal result has occurred from sheer fatigue. This point has been contradicted by other authors, who have found the blood coagulated after these forms of death. Morgagni has described the blood as quite fluid after death in only four instances; all these were cases in which death ensued from slow arrest of the respiration. Drs. Peters, Goldsmith, and Moses, three American physicians, have published a report on the appearance of the blood in seventy cases of death resulting from the excessive use of ardent spirits. In every case, the blood was fluid and dark, was of a cherry-juice appearance, and shewed no tendency to coagulate. Magendie produced a fluid state by injecting putrid matters into the veins of animals. In deaths from the narcotic poisons, from delirium tremens, typhoid fever, and yellow fever, the blood is generally described as thin and uncoagulable. Dr. John Davy found the blood fluid and uncoagulable on exposure, in cases of drowning, hanging, suffocation from the fumes of burning charcoal, and effusion of blood into the pulmonary air cells. Mr. Gulliver narrates an instance, in which a man and his three children were suffocated in a burning house. In all, the blood in their hearts was fluid, and remained so permanently. In a case of hanging, Mr. Gulliver met with the same fluidity; but in kittens killed by hanging and drowning, he has seen coagulated blood in the heart.

In cases of an opposite type, viz. acute inflammatory disorders, hyperinosis, the blood has generally been described as firmly coagulated, or with the fibrin more or less separated in the form of concretion.

Altogether, the experience and observation of the majority of writers tend mainly to sustain the following conclusions.

1. That in cases where immediately previous to death the fibrin is increased in quantity (whether from active hyperinosis or from a relative excess of the fibrinous constituent), coagulation is firm, and the disposition for separation of fibrin, in the form of concretion, is well marked.

2. That in some cases, where the blood current is impeded, as in an aneurism, or in the heart where the valves are rigid, or in very feeble states of the heart, the fibrin has a tendency to separate from the other blood constituents, at the point of obstruction, and to form itself into distinct masses-fibrinous concretions.

3. That after the introduction of some poisonous agents, as pus, into the circulation, and the death resulting therefrom, there is often a distinct separation of fibrin, and firm coagulation generally.

4. That, in instances where the death of the body is produced by an interference with the natural chemical interchanges between the blood and oxygen, as from impeded respiration, great fatigue, the use of ardent spirits, and the inhalation of volatile narcotic agents, as carbonic acid, the process of coagulation is often materially retarded, and is imperfect.

5. That in some special diseases of the hypinotic class, such as scurvy and typhus, the consistency of the blood is diminished, and its coagulation in a great degree prevented.

6. That in instances where death occurs from the abstraction of water from the blood, as in cholera, the entire fluid is left in a dark, tarry, and semicoagulable