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of such paralysis must be relaxation and dilatation of the tubes. Now, their ultimate ramifications open into the air-cells by apertures which are of less diameter than the air-cells themselves. Thus, under normal conditions it may be said that the air-cells form as it were an ampulla at the extremity of every twig of the bronchial tree; and this arrangement evidently affords the conditions requisite for the generation of a sonorous veine fluide at each of these points. But when the pneumogastric nerves are divided, the relaxed and paralysed bronchial tube opens into the air-cells by a funnel-shaped aperture. Hence, the respiratory murmur is no longer audible.
It is evident that this view with regard to the origin of the pulmonary inspiratory murmur is not essentially different from that which was propounded in this 'Review' in the year 1865, by Dr. Waters.
"The air-sacs," says Dr. Waters, “ consist of somewhat elongated cavities, which communicate with a bronchial ramification by a circular opening which is usually smaller than the cavity to which it leads, and has sometimes the appearance of a circular hole in a diaphragm, or as if it had been punched out of a membrane which had closed the entrance to the sac.
I believe that in the passage of the air through this constricted opening the main elements of the respiratory murmur consist."
According to this theory, therefore, the sounds heard during respiration have two distinct seats of origin :-(1) The glottis; (2) the termination of each minute bronchial tube in the corresponding air-sacs. During expiration, on the other hand, the conditions requisite for the development of a veine fluide within the lungs do not exist. In escaping from the pulmonary tissue into the bronchial tubes the air passes from a wider into a narrower space. And although each division of the bronchial apparatus opens into a larger tube, it must be borne in mind that the section of every tube is always less than the combined sections of the smaller tubes that open into it from below. Bondet and Bergeon, accordingly, agree that in their experiments, when the trachea was freely incised and drawn out through a wound in the neck, all expiratory sound ceased over the surface of the chest. We can, therefore, understand why in the human subject the expiratory murmur should either be entirely absent, or should at any rate be much less intense than the inspiratory under normal conditions ; in fact, no expiratory murmur exists, except that which is transmitted downwards from the larynx.
Before quitting this part of our subject, we must add that M. Luton, while admitting the accuracy of M. Bondet's facts, is, nevertheless, disposed to doubt the validity of his explanation
that the pulmonary inspiratory murmur is due to a veine fluide formed by the air in passing from the extremity of a bronchial tube into the relatively larger air-cells. “It is doubtful,” he says, “ whether we can apply rigorously the law of analogy to such extremely minute canals." M. Luton goes on to point out that in respiration the air is energetically drawn into the lungs by the movements of the thorax, and thus, as it were, into a vacuum. Thus, in each part of the respiratory passages the air has a tension greatly in excess of that which exists in the parts beyond. And he conceives that this inequality of pressure may lead to the development, in the whole extent of the air-passages, of a series of alternate waves of condensation and rarefaction, by which sound may be generated. Indeed, just as we have maintained that no physical experiments have as yet reproduced the conditions afforded by a contracting cavity (such as the cardiac ventricle), so we may admit that the phenomena attendant on the suction of air into organs like the lungs are, after all, imperfectly imitated by simply forcing gases through tubes. It may be that in the act of inspiration physical laws, by which sound is generated, are called into action, altogether apart from those which regulate the development of veines fuides.
We may now pass on to consider how these views with regard to the respiratory sounds may be made to bear on the auscultatory phenomena presented by the air-passages and lungs under various diseased conditions. And first we must remark that the theory of M. Beau, as originally enunciated, was intended to include "all the respiratory sounds, not complicated with râules," and was by no means limited to the normal inspiratory murmur heard over the surface of the lungs in health, to which murmur alone Dr. Stokes and Dr.Williams directed their critical remarks on the theory. Indeed, the observation which originally led M. Beau to doubt the correctness of the commonly received views was the following: -He was examining a case of pleuritic effusion, in which the subspinous fossa presented marked tubal respiration, so that it seemed to blow into his ear. At the same time the patient was making a loud noise in breathing. But when he was told to breathe quietly so as to lessen this noise, the tubal respiration diminished in the same proportion. M. Beau goes on to say that in several other cases in which a bronchial souffle was audible he found that it could be diminished or suspended by making the individual diminish or suspend the respiratory sound in the throat. He, therefore, concluded that the morbid sound in question is solely due to the transmission downwards of his bruit guttural;" it being of course supposed that hepatized lung, or lung compressed by fluid, conducts sound better than the healthy pulmonary tissue.
As we have seen, the investigations of MM. Chauveau and Bondet have demonstrated the incorrectness of M. Beau's theory as applied to the normal inspiratory murmur. But it would seem that these observers have proved the same theory to be true, so far as concerns the morbid sound, known as bronchial or tubular breathing. A horse was affected with pneumonia, and an intense “ souffle tubaire” was audible. MM. Chauveau and Bondet cut across the trachea below the glottis. The air then entered the lungs without passing through the glottis, and the souffle at once disappeared.'
It is most desirable that the accuracy of this observation should be tested by further observations in the human subject; that it should be ascertained, for instance, whether, after tracheotomy for laryngeal phthisis, bronchial breathing hitherto audible over consolidated parts of the lungs disappears. Perhaps this may not necessarily be the case, for the diameter of the canula used in tracheotomy is much less than that of the trachea, and the conditions, therefore, still exist which are required for the production of a veine fluide. But the experiment of MM. Chauveau and Bondet certainly appears to show that when there is an artificial opening into the larynx it is quite possible that pulmonary consolidation may exist without revealing its presence by the ordinary signs. Perhaps, indeed, this difficulty may not be confined to cases in which tracheotomy has been performed. Ulceration of the larynx, destroying the attachments of the vocal cords, may sometimes prevent the formation of a veine fluide in the air which passes the glottis, and so remove one of the conditions necessary for the development of bronchial breathing in diseased parts of the lung below. In this way we may find an explanation of the fact, on which Dr. Stokes formerly laid so much stress (and for which he admitted that he was unable to account), that it is often difficult or impossible to determine whether the lungs are or are not healthy in cases of laryngeal disease. The fact itself, must, we think, be well known to every practical physician.
The theory of the origin of bronchial breathing in the transmission downwards of sounds produced in the larynx has another practical application of some importance. We believe that most auscultators, in investigating the state of the lungs,
1 We feel bound to state that we have not been fortunate enough to find this experiment recorded either by M. Chauveau or M. Bondet, in their respective papers. We give it on the authority of M. Bergeon, who mentions it in both his works—in the one at p. 18, in the other at p. 15.
Op. cit., p. 253.
direct the patient to breathe as noiselessly as possible. And when he is making a blowing noise with his mouth they attach but little importance to any bronchial breathing that may be audible. Now, our own observations have repeatedly shown us that this is a mistake, although we were not until lately aware of the physical theory which explains why it is so.
It is important to note that M. Beau's theory of the cause of bronchial breathing is not necessarily applicable to the sounds heard over a pulmonary cavity, communicating freely with a bronchial tube. The orifice of the tube then presents the conditions requisite for the development of a veine fluide in the air passing into the cavity. The same remark applies to the fistulous opening which leads into the pleura in cases of pneumothorax. Thus, both amphoric and cavernous breathing may be produced in the spaces over which they are heard. It is, however, necessary for the generation of morbid sounds in this way that the walls of the cavity should not be too rigid, to allow of its undergoing changes of size during respiration, and so permitting the entrance and exit of air. Moreover, it is only during inspiration that a veine fluide can be generated in a cavity in the way we have supposed. According to M. Beau, indeed, the cavernous souffle, equally with the bronchial, disappears when the patient breathes quietly, so that no noise is produced in the throat.
It remains for us to consider how far the theory which we have been considering applies to the auscultatory phenomena presented by emphysema of the lungs. The writers whose works are under review have, however, made but little reference to this disease, perhaps because they have found some difficulty in dealing with it. Dr. Waters, indeed, finds an argument in favour of his view with regard to the nature of the respiratory murmur, in the fact that in emphysema of the lungs the inspiratory murmur is extremely feeble. The air-sacs, he says, become much altered in character, in consequence of distension, rupture, and absorption; and the membrane guarding the entrance to them entirely disappears as the disease progresses. Bergeon, again, attributes the feebleness of the inspiratory mumur, which Bondet observed in animals after section of the pneumogastric nerves, to the fact, pointed out by Bernard and Longet, that by this operation the lungs are rendered emphysematous. Hence, says Bergeon, the air which enters the chest, finding the pulmonary vesicles already distended, cannot penetrate them with the same degree of force as before. But it is to be observed that the inspiratory sound is equally deficient during an attack of asthma. Now, in this disease, according to the theory current in England, the bronchial tubes are narrowed by spasmodic contraction; and one might, therefore, suppose that they would fulfil better than tubes in the natural state the conditions required for the development of a sonorous veine fluide.
A more serious difficulty seems to be presented by the prolonged expiratory murmur, that is well known to be so marked a feature of emphysema and of capillary bronchitis. Luton, indeed, attributes this to the transmission downwards of a sound formed within the larynx. It is, he says, the first phase of the same phenomenon, of which an extreme degree constitutes the souffle tubaire. The expiratory sound of emphysema, prolonged as it is, is not more sonorous than natural, unless the laryngeal murmur is itself increased in intensity. We cannot but regard this explanation as extremely unsatisfactory, and as failing to meet the facts of the case.
III.-A System of Dental Surgery.' PERHAPS there is no speciality in surgery which has made greater advances within the last ten years than that concerned with diseases of the dental organs, and the issue of a second edition of a book which has been generally accepted as an authority for those engaged in the study of dentistry presents a fitting opportunity of reviewing the progress made. The treatment of the teeth was for many years to a great extent empirical, and too often carried on by men who had but little general education and who were for the most part medically unqualified; but a noble effort on the part of those whose exertions in its cause have made odontology a science caused the College of Surgeons to recognise its claims by granting a special licence in dental surgery. This diploma is the more valuable inasmuch as it implies that its possessor has spent two years in study at a general hospital, attending the same lectures, and engaging in the same curriculum as that which is necessary for those who desire to obtain the full qualification in medicine and surgery.
The higher qualifications required have already materially improved the class of men who enter the profession; and although it is a question whether it would not have been a wiser measure to have
a given the degree of licentiate in dental surgery only to those who had qualified themselves by becoming members of the College, the necessity of spending two years at a hospital amongst those who are qualifying themselves for higher degrees stimulates the
' A System of Dental Surgery. By JOHN TOMES, F.R.S., &c., and CHARLES S. TOMES, M.A., &c., &c. Second edition, revised and enlarged with 268 en. gravings. London, 1873.