already exceeded. Nor can we deal otherwise with the section devoted to the consideration of organic matter in the air.

'Air and Rain' might be the name of a romance, so odd are the names which now-a-days are chosen by novelists. We know, indeed, of a sea-story, for which the title of Wind and Water' was contemplated. If any one, however, happens to send to the library for the work under notice, in the expectation of getting back a piece of light reading, it will be unfair to examine too strictly the words in which his disappointment is likely to find expression. Ordinary blue books are altogether Braddonish in comparison with this great record of ill-assorted, half-digested, dry facts,-a record which, notwithstanding its faults, will find an honourable place in every good library of reference.

It falls to few men to raise such a pile of original observations -even though the structure does resemble that of the cairn more than that of the well-coursed and well-jointed pyramid-yet the raiser of the pile in question modestly calls it "this beginning." Does he himself hope and intend to give us the ending of this beginning? We can scarcely think so, but we are ready to believe anything of the boldness of a man who is able to say"I have an actual pleasure in east wind."

II. On the Physical Theory of Murmurs, Vascular, Cardiac, and Respiratory.1

THE second volume of the Lancet,' published in the year 1828, opens with a short essay, by Dr. (now Sir Dominic) Corrigan, entitled "An Inquiry into the Causes of Bruit de Soufflet' and Frémissement Cataire."" The views propounded in this paper have quite recently received corroboration and extension at the hands of certain eminent French physiologists, and have been applied to a large number of auscultatory phenomena. We think, therefore, that our readers can hardly fail to be interested in a brief résumé of the subject.

11. Théorie des Bruits Physiologiques de la Respiration. Par le Dr. L. BERGEON. Paris, 1869. Pp. 20.

2. Des Causes et du Méchanisme du Bruit de Soufflet. Par le Dr. BERGEON. Paris, 1868. Pp. 103.

3. Nouveau Dictionnaire de Médecine et de Chirurgie Pratiques. Art. "Auscultation." Par ALFRED LUTON. Paris, 1866. Pp. 122.

4. Etude sur la Respiration; Recherches Physiologiques sur le Méchanisme des Bruits respiratoires. Par M. le Dr. BONDET, Médecin de l'Hôtel Dieu de Lyon. Gazette Hebdomadaire,' 1863, p. 798, et seq.

5. Études Pratiques sur les Murmures Vasculaires, ou Bruits de Souffle et sur leur valeur Séméiologique. Par M. A. CHAUVEAU, Sécrétaire adjoint de la Société Impériale de Lyon. Gazette Médicale de Paris,' 1858, p. 247, et seq.

Laennec had maintained, as the result of his observations and experiments, that bruit de soufflet is owing to a true spasmodic contraction of the heart or arteries. This view is opposed by Corrigan, partly by reasoning, partly by the following experi

ment:

"Apply," he says, "the stethoscope under the outer third of the clavicle, not allowing it to pass on the subclavian. In a strong healthy man, not agitated, the mere impulse of the vessel is felt. Now compress the artery above the clavicle, so as to diminish the flow of blood through it; a loud bruit de soufflet is heard. Make strong pressure so as effectually to stop the flow of blood; no sound is heard. If the sound in this experiment arise from the arterial tube being excited into muscular action by the stimulus of the pressure, why does it cease when the stimulus is increased? If it be owing to spasm, it should be expected to continue at least some short time after the stimulus has been removed, or, the artery becoming accustomed to the pressure, if continued, its effect as a stimulus should cease. Neither takes place."

And a little further on he gives the following explanation of the production of the bruit in the experiment just described:

"When an artery is pressed upon, the motion of the blood in the artery immediately beyond the constricted part, looking from the heart, is no longer as before. A small stream is now rushing from a narrow orifice into a wider tube, and continuing its way through surrounding fluid. The motion is that of a current; the sides of the artery, instead of being acted upon by a body of fluid moving forward almost as a solid mass, receive the impulse of a stream whose particles are in motion with different degrees of velocity. The rushing of the fluid is combined with a trembling of the artery, and the sensation to the organ of touch is the frémissement of Laennec, the bruissement of Corvisart, and to the sense of hearing 'bruit de soufflet.'"

And he goes on to show that, in aneurism, and in narrowing of the auriculo-ventricular communication in the heart, similar conditions are met with, that the effect on the blood's motion is the same, and that the bruits heard in those diseases are fairly referable to the same causes, as in the experiment above described.

Before concluding his paper, Corrigan feels it to be necessary to meet by anticipation the objection that he has "fallen into the errors of the mechanical physiologists, in ascribing to physical causes phenomena taking place in the living body." How different must have been the tone of physiological thought then from that of the present day! We should now feel it to be the crowning proof of the adequacy and completeness of a physiological theory to include it within the scope of a physical law. This has since been done, in the case of the arterial bruit, by

several French writers, who have shown that it is a particular instance of a phenomenon long ago fully investigated by Savart, and designated by him the "veine fluide" or "veine liquide," terms for which the German equivalent is "Pressstrahl," while the expression "fluid vein," is used by some English writers. And, perhaps, the best account of the matter is found in the work of M. Bergeon, which we have placed at the head of the present article.

"Whenever a liquid flows from a reservoir, through a vertical or horizontal orifice, the stream takes the form of a jet, to which Savart gave the name of a 'fluid vein.'

"The fluid vein' is essentially composed of two parts, the first calm, transparent, like a stem of crystal; the second agitated, without transparency, but so far possessed of regular form that it can be seen to be divided into a certain number of elongated swellings (of which the maximum diameter is always larger than that of the orifice), separated by narrower portions. This nodal appearance of itself shows that the liquid vibrates, and by means of the electric light Savart showed that the flow is not really continuous. The 'fluid vein' in part consists of separate drops of the fluid, succeeding one another at regular intervals, each drop changing its form in passing from point to point."

Thus, then, whenever a liquid escapes from a narrow orifice with a certain amount of force, its flow is intermittent and periodic instead of being continuous, and sonorous vibrations are generated.

The cause of this phenomenon has excited much discussion among physicists, and even now cannot be regarded as settled. Savart showed that it is not due to the vibration of the margin of the aperture through which the jet flows, and that it can be attributed only to oscillations of the entire mass of the fluid within the reservoir, causing that portion of the fluid which is opposite the centre of the orifice to rise and fall periodically, in alternation with the portions of fluid corresponding to its periphery. Bergeon has somewhat amplified this view, but without adding essentially to it.

Now, it is well known that a "fluid vein" is formed not only when fluid is allowed to escape through an orifice into the open air, but also when this orifice opens into a space containing fluid. In other words, if a tube through which a full stream of fluid is noiselessly flowing be constricted at any point, a vibrating "fluid vein" will at once be generated in the wider space beyond. Bergeon gives diagrams, by which the explanation of this is made manifest. By means of manometers it can be shown that above the constricted part the pressure of liquid is much higher than when no obstruction exists. Immediately below the seat of constriction the pressure suddenly becomes

nil; it then very rapidly rises again, but not so high as before, and after this falls suddenly towards the free end of the tube. In passing through the narrowed orifice, therefore, the fluid is in fact passing into a space in which there is no pressure.

It did not escape Corrigan's notice that the conditions which he believed to be requisite for the production of the bruit de soufflet might be imitated experimentally, by passing a stream of fluid through a tube, and he relates the following experi

ment:

"One end of a length of small intestine was attached to a pipe, and a current of water of considerable force was allowed to run through it. While the intestine was kept full and tense, the finger laid upon it received no sensation, any more than if it were laid upon a portion of the same intestine containing fluid at rest; but constriction being made upon any part, then immediately above the narrowed part where the intestine was no longer tense, and where, for the reasons already gone into, the motion of the fluid became very different from that through the upper part of the tube, a sensation was felt precisely like that of the frémissement cataire. No similar sensation was felt above the constriction. The same thing took place with the sound heard by the stethoscope. While the intestine was tense no sound, or a murmur exceedingly indistinct, was heard, but any part being constricted, so as to produce an alteration in the motion of the fluid, a very loud bruit de soufflet immediately became evident."

By Bergeon similar experiments have been repeated and variously modified. And he shows that, whatever the form of the constriction in a tube through which fluid is passing, a "fluid vein," and with it a bruit, is always produced in the space immediately beyond the narrowed point.

But to the physician these experiments will probably seem to be less important than those made on horses by Chauveau, and described by him in a memoir which forms the starting-point of the modern literature of this subject. One of these is the following:-A horse was pithed and the heart was exposed, artificial respiration being kept up. A thread was next passed loosely round the base of the pulmonary artery. Chauveau then introduced his finger into the artery through a small cut in its walls. Not the least vibration could be felt. The blood flowed so softly over the finger that only a vague sensation of its current was perceptible. But the moment that the thread was tightened, so as to narrow the calibre of the vessel sufficiently to produce a bruit de soufflet, he instantly found that in the axis of the artery a "fluid vein" was established, the vibrations of which he could plainly feel.

Chauveau sums up the results of his experiments in the following law:

"Bruit de souffle1 is always produced by the vibrations of an intravascular veine fluide, and such a veine is constantly formed whenever the blood passes with a certain force from a narrowed into an actually or relatively dilated part of the circulatory system."

The author of this theory, therefore, is not satisfied with showing that the veine fluide is a frequent or even a principal cause of the bruit de souffle. He will have it admitted to be the sole cause. We must now inquire what evidence is brought forward, for the purpose of excluding the operation of other agencies, such as roughness of the surface over which the blood flows, alterations in the quality of that fluid, &c.

And we may first take roughness of surface, which has been supposed (in the words of Dr. Walshe) to "cause unnatural friction between the blood and the surface," and so to generate murmur. For the last thirty years this has been placed in the foreground among the causes of bruits. By Gendrin,3 indeed, all valvular murmurs were placed in the same category as pericardial friction sounds under the name of " bruits de frottement endocardiaques." Bouillaud and almost all subsequent writers have maintained a similar view. Now, Chauveau lays it down as a law that a bruit de souffle cannot be generated by mere roughness of the internal surface of a vascular channel, unless the calibre of the tube is modified. Having exposed the carotid artery of a horse, he drew a stout ligature lightly round the vessel at four or five points near one another. The internal and middle coats were torn through, and created a marked roughness of its surface; and this could be still further increased by seizing the vessel with a pair of forceps, and tearing its coats irregularly. But on auscultation afterwards he found that the blood flowed through the artery quite noiselessly; there was no trace of a bruit de souffle. In another experiment Chauveau made the blood of the carotid artery flow through a metallic tube, of the same diameter as the artery itself, with its inner surface roughened; still no murmur showed itself. It must, indeed, be allowed that in experiments of this kind negative results are never in themselves perfectly conclusive, since the conditions cannot be precisely the same as those met with in disease. But for our own part we think that the question

1 It will be observed that some writers quoted in this article use the expression "bruit de soufflet," others "bruit de souffle." It may, therefore, be well to explain that they have exactly the same meaning. The former term was invented by Laennec, and is used by all the writers (as, for instance, Corrigan) whose works appeared soon after Laennec's. Afterwards the latter term was substituted for it, and is now universally employed in its place.

2 A Practical Treatise on Disease of the Heart and Great Vessels,' 3rd edition, 1862, p. 87.

3. Leçons sur les Maladies du Cœur,' 1841-2.

103-LII.

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