condition, but attended occasionally with separation of fibrin in the heart.

7. That in examples of instantaneous death from such causes as shock, suffocation, or lightning stroke, the blood oftentimes, but not invariably, remains fluid in the circulatory system.

COAGULATION OF BLOOD IN THE LIVING BODY.

Of late years, an old question has been revived, whether the blood does not sometimes coagulate in the body during life? This question is now pretty clearly answered in the affirmative. M. Velpeau, in the year 1846, related a case in the Academy of Medicine in Paris, of a woman, from a vein in whose arm a long coagulum of blood had been extracted, and who ultimately recovered. But pathological observations have afforded further evidence in proof, from the condition of the blood in some aneurismal cavities; from the appearance of the arteries, and the formation in them of firm clots of fibrin, in cases of gangrene of the parts which they supplied with blood; and from the construction of the fibrinous masses found in the heart after various discases, together with the symptoms which in such diseases preceded death. From the results of these observations many facts, opinions, and discussions have been elicited by Gould, Templeman, Kerckringius, Tulpius, Pasta, Haller, Morgagni, Götz, Brown, Burserius, Queye, Cullen, Huxham, Corvisart, Stewart, and Chisholm, in a past age; and in the present day by Meigs and Dana, Baron, Fredoult, Bouillaud, Andral, Grisolle, Gaspard, Gulliver, Davy, Burrows, Fuller, Simon, H. Lee, Paget, Crisp, Hughes, Barclay, Corrigan, Fletcher, Kirkes, Hasse, Wagner, and Rokitansky.

I have myself for several years past paid attention to this subject, and have communicated numerous papers upon it, in the affirmative view, to the Medical Society of London. The results of these labours will be given in another place.

From the various arguments and facts put forward by the above numerous authorities, it has been no slight task to make such an epitome as shall fairly represent the meaning and end of their labours. The task, however, has been undertaken, and the inferences obtainable from a review of the whole, to the best of my judgment, are these:

1. That the blood may, in very rare instances, coagulate in the ordinary way, i.e., as a red clot, in the body during life.

2. That the fibrin alone may separate in the form of concretions during life; this result being theoretically attributable (a) to mere slowness of motion, as in the aneurismal tumour; and as in some cases of slow death; (b) to absolute or relative increase of fibrin itself; (c) to a peculiar kind of coagulation arising from chemical or physical changes incident to the mixture of some poisons as pus with the blood; (d) to the neutralisation of those alkaline constituents of the blood, which hold the fibrin in chemical solution, by some free acid, as lactic, generated in the body superabundantly; (e) to an extreme tenuity of the serum in which the fibrin is distributed, with a feeble resistance against the natural attraction of the molecules of the fibrin and their consequent aggregation; (f) to a supposed disorganisation or disintegration of the blood, under the influence of certain diseases, as typhus and scurvy, whereby it has a tendency to divide into its constituent parts.

3. That these depositions of fibrin may, like the buffy coat, differ in constitution; that they may be more or less coloured, from enclosing in their structure modified red corpuscles; that they may become softened in structure, such softening being most marked in the. centre; that they are often accurately moulded to the cavity which contains them; that they may be developed both on the venous and arterial sides of the circulation that they sometimes become firmly adherent to the walls of the heart, by interlacing with the muscular fibres; and that, in some rare instances, the adhesion which they have formed with the heart may become united by vessels, so that the deposit itself ultimately assumes an organised character.

En resumé, we see that in regard to the causes of the coagulation of blood, both in and out of the body, the explanations that have been adduced rest on one or other of three grand theories: the vital, the physical, the chemical; and it is to be observed, that in the order of time in which these theories have influenced physiological inquiries in general, so have they specially influenced those which relate to coagulation. How far each or all of the speculations which have now been recorded have a bearing on the question at issue, is a subject which must be considered in a distinct chapter.

CHAPTER II.

CAUSE OF THE PHENOMENON OF COAGULATION.

PRESENT POSITION OF THE QUESTION.

"The past deserves that men should stand for a time upon it, to view around which is the best way; but when the discovery is well made, they should stand no longer, but proceed with cheerfulness."-LORD BACON.

In the last chapter, I have written simply as the historian, putting together systematically such thoughts and opinions as the learning of previous times has produced on the subject of coagulation, and offering no comments or criticisms thereupon. In the present chapter, I shall reverse this order, taking what has been already written for a text, and discussing it unreservedly, both in detail and collectively.

Fibrin essential to Coagulation. Whatever may be the cause of the aggregation of the molecules of fibrin, the evidence is overwhelming in regard to the fact, that upon this aggregation one part of the phenomenon of the coagulation of the blood depends. This opinion, which I have shewn to have been shadowed forth by Plato, is proved, both on the strength of positive and of negative evidence. The proofs are: first, that if the fibrin is whipped out of the blood, ordinary coagulation does not take place; secondly, that if the fibrin of any quantity of blood rises to the surface, the natural process of coagulation is modified, and the fibrin, blood

corpuscles, and serum, are left in separated conditions, the fibrin only in the concrete form; thirdly, that in a red clot of blood, the corpuscles, and, for some little time the serum also, are retained in the meshes of the fibrin, and that the blood-corpuscles may be washed out of the clot, leaving the fibrin free; fourthly, that the blood corpuscles being removed by filtration, the fibrin will coagulate in the serum, and, contracting more and more, and squeezing out the serum from itself, will remain ultimately a separate and distinct substance.

The question whether or not fibrin exists at all in blood circulating in the vessels of the living body, which some have raised, does not at this point require consideration. For, however much opinions may vary as to the state of the liquor sanguinis during life, there are no differences of opinion as to the fact, that, when blood is drawn, a certain substance, called blood fibre, spontaneously coagulable lymph, fibrin, or by any other name, exists in the blood as a distinct thing; that the particles of this substance possess, under such circumstances, a force of aggregation and contraction; and that to such aggregation and contraction the phenomenon of coagulation is demonstratively attributable, whatever may be the variations occurring in the development of that phenomenon. Further evidence, after facts so obvious, is unnecessary; and hence we start fairly with the general principle, that upon the aggregation of the molecules of fibrin coagulation ultimately depends; and that whatever may solve the problem of the cause of this aggregation, solves at the same time, of necessity, the cause of the phenomenon altogether, as far at least as we can at present foresee.