success, and domestic amities with felicity. The theatre in which he delivered his lectures and expounded his doctrines was crowded with men of science, as well as with pupils, to listen to a youth grown sage by experimental researches."-(P. xviii.) But this happiness was soon to end. He was seized with a fever, occasioned by a wound received in dissection, which proved fatal on May-day 1774, after a short illness, in the thirtyfifth year of his age.

He was buried at St. Martin's-in-the-Fields; but the only record of this admirable physiologist, whose life thus fell a sacrifice to his unceasing zeal for the advancement of science, is a meagre entry in the parish register. Surely some more honorable memorial should hand down to posterity the name and sterling merits of one of the brightest ornaments our profession has ever produced. If the proposition were once judiciously made, we have no doubt funds would readily be found to erect a tablet to the memory of a man equally esteemed in private and in public life.

Subsequently to the death of her husband, Mrs. Hewson continued to enjoy the esteem of Dr. Franklin, the friend of her youth, of which we have a pleasing proof in the following letter, addressed to her from Passy, and bearing date, January 27th, 1783.

"In looking forward, twenty-five years seem a long period, but in looking back, how short! Could you imagine, that it is now full a quarter of a century since we were first acquainted? It was in 1757. During the greatest part of the time I lived in the house with my dear deceased friend, your mother; of course you and I conversed with each other much and often. It is to all our honours, that in all that time we never had among us the smallest misunderstanding. Our friendship has been all clear sunshine, without the least cloud in its hemisphere. Let me conclude by saying to you, what I have had too frequent occasions to say to my other remaining old friends. The fewer we become, the more let us love one another."-Introd. p. xx.

After Mrs. Hewson lost her mother, and in compliance with the frequently expressed wish of Franklin that she should become his neighbour in America, she went with her children to Philadelphia, and died in 1795, leaving two sons and a daughter. The second and surviving son, Dr. Thomas Tickell Hewson, is, according to inquiries lately made by Mr. Gulliver, still alive, and is the President of the College of Physicians at Philadelphia.

Having given this brief biographical notice, which we are assured our readers will agree with us was a proper tribute to the memory of such a man as Hewson, we proceed to the consideration of his scientific labours, the principal of which relate, as it is well known, to the blood. In order to do justice to these researches, it will be necessary to enter somewhat fully into the properties of the circulating fluid: we trust, however, that this detail may not be devoid of interest in another point of view, as the volume before us is enriched by copious notes, in which the judicious editor has brought together a large amount of important matter, collected from various sources, his own inquiries forming a very valuable portion of these additions.

The very interesting and comprehensive introduction of Mr. Gulliver, in which he traces the successive progress of discovery in relation to the blood, shows how much we are indebted to Hewson for an exact know

1847]

Estimate of Hewson's Labours.

5

ledge of many of the fundamental qualities of the circulating fluid; and on how many points he had anticipated the results of modern discovery. It is indeed true in this, as in so many other instances, that several facts of great importance had been discovered by earlier observers; but then owing, partly, to the false hypotheses with which they were encumbered; and, partly to the neglect and errors of subsequent writers, the whole history of the constitution of the blood was involved in great confusion when our author commenced his " Experimental Inquiries." Upon this point Mr. Gulliver justly remarks that

"In considering the labours of Hewson in connexion with the facts observed and the errors held by his predecessors and contemporaries, it must be recollected that the speculations connected with Leeuwenhoek's microscopical researches for many years supplanted accurate experimental inquiries into the properties of the blood; so that the fibrin was either forgotten or confounded with the serum, and a fanciful importance was given to the red corpuscles. When the errors consequent on this state of things began to wane, the blood sunk into neglect. Accordingly, the just observations of Malpighi, Lower, and Borelli, were lost for the greater part of a century, while the coagulation of the blood was ascribed to a mere cohesion or running together of the red corpuscles, and the formation of fibrinous clots to a change in the serum. These opinions were held in Britain by the best writers to the year 1760, and on the Continent by the most distinguished physiologists, as Haller and Marherr, up to or even beyond 1771, the date of the first edition of Hewson's Inquiry into the Properties of the Blood.' But there were exceptions. The knowledge of Petit, Quesnay, Senac, and Gaubius, was unquestionably in advance of that current in their day; yet they added but little to the facts of the older observers, so vaguely discussed by Haller, so ably used in the masterly memoir of Petit; and some of the opinions set forth by Quesnay and Senac, partook of that general crudity which proved how necessary it was that the properties of the blood should be studied anew by the experimental method."-Introd. p. xl.

It would be unjust towards a neglected but ingenious observer, Dr. Richard Davies, if we did not state that, in the opinion both of Dr. Davy and of Mr. Gulliver, to this writer, who preceded Hewson by about twenty years, belongs the merit of clearly apprehending the true method of studying the blood, namely, by experimental research. His "Essay," considered as a demonstration of the distinctive characters of the three proximate principles of the blood, is also, we are informed by the same authority, "admirably decisive."

Although the independent existence of these three constituents, the fibrin, the red corpuscles, and the serum, and their relation to the process of coagulation, are for the most part well known, yet, in order to guard against the errors which are even in the present day, from time to time, springing up; and especially for the purpose of adducing a few of those simple but convincing experiments which are a model in this field of research, we quote the following from the first part of the "Experimental Inquiries." Alluding to the inflammatory crust, and to the opinion entertained by some authorities that it is formed by the serum, Mr. Hewson remarks:

"But that it is formed by the coagulable lymph alone, after the red particles have subsided, appears from the following experiments.

"Experiment 11.-In the month of June, when the thermometer in the shade stood at 67°, I bled a man who had laboured under a phthisis pulmonalis for

some months, and at that time complained of a pain in his side. The blood, though it came out in a small stream, yet flowed with such velocity, that it soon filled the basin. After tying up his arm I attended to the blood, and observed that the surface became transparent, and that the transparency gradually went deeper and deeper, the blood being still fluid. I likewise observed that the coagulation first began on the surface, where it was in contact with the air, and formed a thin pellicle; this I removed, and saw that it was soon succeeded by a second. I then took up a part of the clear liquor with a wet teaspoon, and put it into a phial with an equal quantity of water; a second portion I kept in the teaspoon; and I found afterwards that they both jellied or coagulated, as did also the surface of the crassamentum, making a thick crust. On pressing with my finger that portion which was in the teaspoon, I found it contained a little

serum.

"From this experiment it is evident, that the substance which formed the size was fluid after it was taken from the vein, and coagulated when exposed to the air; and as this is a property of the coagulable lymph alone, and not of the serum, there can be no doubt that the size was formed of the lymph." P. 32.

In order further to demonstrate the same fact, Hewson performed many interesting experiments, in which, having observed that neutral salts have the power of preventing the process of coagulation, he availed himself of this circumstance to obtain the fibrin or coagulable lymph, as he terms it, separately from the red corpuscles.

"In these mixtures of the blood with neutral salts, the red particles readily subside, (especially if human blood be used), and the surface of the mixture be comes clear and colourless; and being poured off from the red part, it is found to contain the coagulable lymph, which can be separated by the addition of water." P. 12.

After all these, and a great number of other exact experiments, it is strange that any doubt should subsequently have arisen as to which was the coagulable matter of the blood. We need, however, scarcely remind our readers, that Sir E. Home and Mr. Bauer, reviving what Mr. Gulliver calls the old and discarded hypothesis of Sydenham, contended that the fibrin, instead of being what Hewson had so distinctly proved it to be, an independent constituent, was formed in the act of coagulation by the colourless matter of the red corpuscles. This error, which received little or no sanction from English physiologists, became so prevalent on the Continent, that Professor Müller was deemed to have rendered good service for proving, partly, by the very ingenious experiment of mechanically separating by filtration the red corpuscles from the fibrin in the blood of the frog; and, partly, by repeating some of Hewson's experiments with the neutral salts, that the coagulating material is altogether distinct from the colouring substance. Another theory has also been lately advocated, to the effect that both the fibrin and the albumen of the serum are contained within the pale or colourless corpuscles of the blood; a position which we believe to be utterly untenable. Whether it be true, as some physiologists contend, that these corpuscles elaborate the plastic element or fibrin; or that this change is effected by the red corpuscles; or that the fibrin is formed in some other and at present unknown way, which, considering the chemical relations of that substance and of albumen, may be regarded as the most probable explanation; however this may be, there can, we think, be no reasonable ground for doubting that, once formed, the

18471

Condition of the Blood in Inflammation.

7

fibrin exists as an independent principle, composing, in conjunction with the serum, the fluid portion of the circulating blood, or liquor sanguinis. A point on which Hewson made many valuable observations, relates to the production of the buffy coat; and as this is a subject of practical importance, and one, moreover, that has received much elucidation from modern research, we are desirous of stating the results that have been obtained. It is a striking illustration of the accuracy which characterises Hewson's investigations, that he detected one of the most essential changes of buffy blood, namely, its attenuation, and this in opposition to the prevailing opinion.

"How contrary," he says, "to the conclusion, which these experiments lead us to, are the opinions of some medical writers on this subject! How frequently do we find it said, that the blood is thicker in inflammatory disorders, where that size occurs; and that a large orifice is necessary to let out the vitiated blood! That a large orifice is preferable to a small one in many cases, where such blood is found, I believe to be true; but that its advantages are owing to its letting out the thickened blood, seems improbable from what we have seen in the experiments above related: they are perhaps nearer the truth, who attribute it to the suddenness of the evacuation." P. 40.

He further ascertained the fact, that the red corpuscles sink more rapidly in the liquor sanguinis of buffy blood than in the serum alone; and, putting these circumstances together, it is not a matter of surprize, that he attributed the formation of the sizy coat to the attenuation of the liquor sanguinis, and to the more ready subsidence of the red corpuscles consequent thereon towards the lower part of the crassamentum.

The application of the microscope has thrown a clearer light upon the phenomenon in question; and has shown that the peculiar attraction which, under certain circumstances, the red corpuscles have for each other, and in virtue of which they form the well-known piles or rouleaux, plays the most essential part in the formation of the buffy coat. This piling of the red discs, which is one of the most remarkable, and at the same time beautiful, appearances seen on examining a drop of blood,* was evidently known to Hewson; for he remarks, in arguing for the flat form of the corpuscles, "I have seen them with their sides parallel, like a number of coins laid one against another."-L. c., p. 228.

Dr. Hodgkin and Mr. Lister were the first in the revival of microscopical anatomy, distinctly to describe the disposition just noticed, which takes place in healthy blood during coagulation. But what more particularly concerns the present question is that, in buffy blood, the red corpuscles evince an increased tendency to aggregation; a fact well known to Hunter, who, in speaking of the blood in inflammation, says, "the red globules become less uniformly diffused, and their attraction to one another becomes

* The piling of the corpuscles affords to the inexperienced microscopist, the best idea as to how the red colour of the blood is produced; for it is seen that, when the piles are formed, the so-called red corpuscles, which are, as it is familiarly known, of a pale yellow examined singly, begin from their aggregation to reflect the red ray, and to assume a pinkish tint; and that where two rouleaus lie across each other, the tint becomes deeper; till at last, where several piles are heaped together, the ordinary red colour of the blood is produced.

stronger;" so that the blood, when out of the vessels, soon becomes cloudy or muddy, "and when spread over any surface, it appears mottled, the red blood attracting itself and forming spots of red.' In this passage, as Mr. Gulliver justly remarks, Mr. Hunter has anticipated some recent observations; and if he had employed the microscope, which instrument, however, there is reason to suppose, he did not use, he would have seen, as Dr. H. Nasse was the first to show, that in buffy blood the red corpuscles more readily run together into piles, and, consequently, separate from the fibrin more completely; circumstances which are apparently favoured by the diminution of the corpuscles, and the increase of the fibrin occurring in inflammation. It is then this augmented attraction of the blood-discs for each other that ought to be regarded as the essential condition on which the sizy coat depends; though there is no doubt, as Mr. W. Jones has explained, that the massing together just noticed, increases the specific gravity of the corpuscles, considered in the aggregate, and thus allows of gravitation coming into play as a secondary cause. This is well put by Mr. Gulliver, who remarks, "in buffy blood, they (the corpuscles) are still more closely connected, almost as if fused together, and the piles run into little clumps often visible to the naked eye. Now we know that coarse particles sink more rapidly in a liquid than fine ones, and the clumps of corpuscles in buffy blood represent much coarser particles than their composing single piles or separate corpuscles. The more they run together, therefore, the faster they will fall in the liquor sanguinis, so as to produce the buffy coat. Accordingly, it was found in my experiments that, during the formation of the buffy coat, the corpuscles will at first take about two and a half minutes to sink an eighth of an inch in the liquor sanguinis, and fall five or six times faster in the next two or three minutes; and that this remarkable acceleration in the sinking of the corpuscles is connected with their increasing aggregation, appeared from the fact that their rapidity of sinking was increased by increasing their aggregation, though the means used did not attenuate the blood; and prevented or even reversed by destroying the aggregation, though by means which made the blood much thinner and lighter."-P. 41, Note xxiii.

In connexion with this subject, it may not be superfluous to notice that the buffy coat, although so frequently an accompaniment of inflammation, is not to be regarded as an invariable sign of that state; thus it occurs regularly in the blood of the horse, and also, as it is well known, in the advanced stage of pregnancy. In these instances there is an excess of fibrin, and it is probable that this circumstance may, as the majority of writers suppose, favour the formation of the buffy coat. It may, also, be as well to state that the peculiar piling together of the red corpuscles is not confined to the coagulating process, having been observed by several microscopists to supervene in the small vessels of inflamed parts, producing an appearance in the stagnant blood, as if the corpuscles were fused together; and unless the circulation is restored to its normal state, doubtless influencing, in an important manner, the subsequent phenomena.

There is no part of these works which may be perused with more advantage than that which treats of the influence of faintness on the process of coagulation, and of the principles that should be observed in the treatment of hæmorrhage. It seems that Hewson was led to investigate this subject