Fibrine may undergo alterations in quality during disease. In the healthy state it is com posed of definite quantities of oxygen, hydrogen, azote, and carbon • and it ik quite possible that some variety in the proportion of these consti tuents may give rise in disease to morbid states of that principle. Huxham observes that in malignant petechial fevers the 'crasis is so broken as to deposit a sooty powder at the bottom of the vessel, the upper part being either a livid gore, or a dark green, and exceedingly soft jelly. De Haen saw the blood in a dis solved state, and in the plague the blood is said not to coagulate.
In some persons there exists a state of con stitution, bordering no doubt upon passive hw morrhagic disease, in which the blood is ob served either to coagulate very imperfectly or not at all. Alarming haemorrhages from the slightest wounds are the consequence of such a diathesis, and the most powerful styptics will not always succeed in preventing their fatal termination. Dr. Wardrop, in a small work just published, has collected together several interesting cases of this kind, and from some of these it is demonstrated that such a condition may exist in many members of the same family, and even sometimes become hereditary.
In the dead body blood is sometimes found in a liquid state, resembling water, holding in suspension a red, brown, or black colouring matter. In this case, according to M. Andra!, it has been demonstrated chemically that it still contains fibrine, but altered in its character, so as to be no longer coagulable. This dis solved state of blood observable after death is probably the same as that which exists in sea scurvy, in putrid and typhous fevers, and in the latter stages of fatally terminating diseases characterized by defective nervous energy. It is matter of more common observation, how ever, that fibrine alters materially in its relative quantity. We often find that the clot is large in proportion to the serum, may indeed arise from its being loose and defective in con tractility, so as to contain a large portion of fluid, or from its holding entangled among its meshes an unusual number of red particles ; but it will often also arise from there being a more than ordinary quantity of fibrine present, in which case it will be firm and contractile as well as voluminous. Blood thus circumstanced is said to be rich and thick, and is generally met with in those whose complaints are con nected with a plethoric habit.
A deficiency in the proportion of fibrine is likewise not unfrequent among those who suffer from complaints of debility, or who have lost much blood by natural or artificial depletions. In this case the clot is small, and has but little contractile power.
It is, I conceive, a possible case, that the fibrine may separate imperfectly or not at all, in consequence of an augmented proportion of salts, which out of the body we know to be capable of suspending coagulation altogether.
The continued use of alkaline remedies will probably tend to. produce a like effect.
Fibrine coagulates the more speedily in porportion as the circulating and nervous sys tems become more feeble. The experiment has been repeatedly made with animals that are killed by bleeding, and the last por tions of blood invariably coagulate soonest. " The principle of the blood's speedy con cretion in debility is important in a curative point of view. The first natural check to hae morrhage is known to be the formation of a clot on the mouth of the vessel. If the longer the hmmorrhage the less had been the disposition to form such a clot, the on the field of battle, and those injured by common accidents, who cannot promptly procure the aid of a surgeon, must inevitably have perished." One of the most remarkable and frequent de viations from the normal condition of blood removed from the body by venesection, is the occurrence of the buffy coat, which is a layer of fibrine occupying the surface of the crassa mentum. The blood, whilst circulating within its vessels, consists, as I have already remarked, of a fluid which I have elsewhere ventured to call liquor sanguinis, and of insoluble red par ticles. These being in constant motion are uniformly diffused throughout this liquor; but their specific gravity being much greater than that of the medium in which they are sus pended, they have a tendency to gravitate when ever that motion ceases. In healthy blood the fibrine coagulates so quickly that the red par ticles have not time to subside, so as to leave any portion of the liquor entirely free from them. By protracted fluidity this result is effected; the red particles do then gravitate to a greater or less depth before the liquor separates into two parts. A general coagulation of the fibrine at length occurs, and a clot is formed. That part of it through which the red particles had fallen becomes a layer of fibrine free from colour, and merely having some serum mecha nically retained in its meshes, while the sub jacent portion is of intense depth of shade, especially at the bottom, and of less than ordi nary cohesion. In extreme cases, such an abundance of red particles reaches the bottom of the vessel that they are there found in a state of fluidity. The buffed layer sometimes assumes a cupped form, which is clearly owing to unequal contraction. The upper surface being freer from intervening red particles, con tracts more powerfully than the under, and a concavity of the surface is the necessary con sequence. Where, however, the contraction is weaker, the weight of the subjacent red clot, which is one and the same mass with the upper colourless portion, weighs this down, and keeps it in a horizontal position.