COAGULATION OF THE BLOOD.

CHAPTER I.

HISTORICAL MEMORANDA ON THE SUPPOSED CAUSES OF THE COAGULATION OF THE BLOOD.

"Every physician will and ought to make observations from his own experience; but he will be able to make a better judgment and juster observations by comparing what he reads and what he sees together. The searcher of authors has the benefit of other men's experience as well as his own, and it is by the joint concurrence of these that we can hope for any considerable advancement in knowledge. Were it not for this, the oldest practitioner would always be the best physician, and there would be little difference, even as regards the scientifical part, betwixt an old woman and the most regular professor."-FRIEND.

It is not my intention in this chapter to follow up in chronological order the labours and discoveries of those who, either in ancient or in modern times, have endeavoured to solve the problem of the cause of the Coagulation of the Blood. My object in these memoranda is simply to collate the various theories and hypotheses, which have been advanced regarding coagulation. The authors, advocates, or opponents of such theories or hypotheses will, however, receive attention incidentally, as they may have originated, supported, or opposed the various opinions or arguments which have to be narrated. It will be my endeavour to condense what has here to be said, as far as is consistent with plain writing and with fairness of description; while, to prevent the interruptions which always

occur to the reader from repeated references to footnotes, the works of the authors mentioned, as the history proceeds, will be tabulated at the end in an alphabetical list. Should it happen that the views of any writer are omitted, I crave pardon, and explain that as this essay is mainly the record of an original inquiry, no strain has been made towards historical display. I place before the reader, in fact, in acknowledgment of good and learned assistance, the names merely of such authorities as have answered fully to certain matters of fact and argument, which I was anxious to obtain before embarking in original work, and to bear in mind afterwards. For I hold it as a rule, that no one can pursue an original inquiry, who does not know that true originality of thought includes two principles; the one consisting in a knowledge of what is not original, i. e., of what has been done; the other in an appreciation of what remains to be originally done, and how to do it.

The subject of the coagulation of the blood did not escape the attention of the old physiologists of Greece; and even at the early period when they lived, the cause of this phenomenon was supposed to depend on a net-work or fibre in blood, which, by coming together and contracting, gives rise to coagulation-a supposition which has been sustained to the present day. Plato, in his Timaus, very distinctly remarks, that throughout the blood are scattered a number of fibres, which give to the fluid certain measures of tenuity and density; so that it may neither flow through the "thin" structures, nor, from its density, become unadapted to motion, and thus find a difficulty in flowing back by the veins. And he further observes, that the blood is

under the natural guardianship of the fibres; because, if these are collected together in dead blood, all the remaining blood becomes diffused; and when blood is let out quickly, it coagulates in consequence of the cold surrounding it.

Dr. John Davy points out also that Aristotle paid attention to the same question, and considered that a substance in the blood, which we must believe to be the same as that now called fibrin, is liquid so long as the blood is in motion in the living body, like the matter of curd in uncoagulated milk, and solid only and fibrous after extraction, the coagulation being the effect of the change.

The process of coagulation did not, however, receive much further attention until the Harveian discovery of the circulation. This discovery acknowledged, certain pathological states of the blood became subjects of special study; and Malpighi was led to discover and point out accurately the fact, that the buffy coat is made up of a substance natural to the blood, its concrete or reticulated part, and identical with the white clots not unfrequently found after death in the circulatory system, and particularly in the heart.

Again, even for a long period after Malpighi, great confusion existed regarding the different parts of the blood. A few observing men, it is true, distinguished correctly the differences between corpuscles, serum, and "spontaneously coagulable lymph", but their views were not accepted. By other men, serum and "spontaneously coagulable lymph" were confounded as one and the same. By a third and more numerous body, this lymph was ignored altogether, and the globules were turned to as everything, so that the phenomenon of coagulation was

considered merely to consist in an aggregation of these, brought about by some force of attraction. There is not a more interesting historical subject in physiology than the one here noticed. But I do not discuss it at length, because Mr. Gulliver, in his introduction to Hewson's works, has said all that can be said, with such masterly judgment, candour, and critical learning, that it were impossible to dwell on the topic without trespassing on his domain.

Referring to the views, correct, at least, in part, of Malpighi, Lower, Borelli, Boyle, Collins, Ruysch, Petit, Butt, Glaubius, and Quesnay; and to the incorrect and confused views of Leeuwenhoeck, Boerhaave, Haller, and Senac, Mr. Gulliver shews that the speculations connected with Leeuwenhoeck's microscopical researches supplanted accurate experimental inquiries into the properties of the blood. When, therefore, “the errors consequent on this state of things began to wane, the blood sank into neglect, and the just observations of Malpighi, Lover, and borelli were lost for the greater part of a Century." In England. the errors continued to the year 1760; on the continent, even later than 1771, the year when Hewson first published his labours. To Dr. Kelard Davies Mr. Gulliver assigns the credit of

Laving revivel and established that correct knowLodge of the three parts of the blood which was taught afterwards by Hewson, Fordyce, and the Hunters." This may be so; and, indeed, Hewson himself laid no claim to the discovery of the constituent parts of the blood, but I take it, that he (Hewson) held more correct views on this matter than any of his predecessors. He described the red or colouring part-red corpuscles; the lymph, or spontaneously coagulable part-fibrin (so called

thirty years later by Fourcroy); and the serum; the latter containing, as he taught, a constituent which, agreeing with the white of egg, remains fluid when exposed to the air, but coagulates when exposed to heat-albumen. It is but fair, moreover, to give to Hewson the credit of having been the first to demonstrate that the transition. of the coagulable lymph from the liquid to the solid state, is an essential and independent part of the process of coagulation. This view was theorised on before; but was not proved by experiment until Hewson skimmed off the size from the blood of a phthisical patient, and observed its spontaneous separation into colourless clot and serum.

Since 1771 there has been confusion again; some sort of retrogression towards Leeuwenhoeck's speculations; some progression, without experiment, into profound and mystical controversies and descriptions. So science, like the great ocean, fluctuates; but, by fluctuating, encroaches and advances, her vitality and sign of existence being her unceasing unrest. At the present moment, Hewson's definition of the parts of the blood is the one generally accepted.

Historically, then, we start with the knowledge, that the first true steps in the problem on which we are engaged have consisted in the discoveries of the "bloodfibre" (in this day called fibrin); of the tendency of this fibre to coalesce under certain favouring conditions; and of this coalescence as one cause of the phenomenon of coagulation. The next step in the inquiry, Why does the fibrin concrete at all? is continued to modern times, and opens for consideration numerous experiments, theories, and hypotheses.