this accumulation is directly connected with the spasmodic derangement which produces the paroxysm. The connection of these two phenomena it is by no means difficult to understand, according to the principles already laid down; in fact, if the removal outwards of the pulmonary mucus depends, in the normal state, upon the regular peristaltic contraction of the bronchial muscular fibres, it is obvious that accumulation must accompany the derangement of that action, just as constipation is the invariable concomitant of the analogous derangement of colic or ileus. In both cases the paroxysm ceases when the normal action is restored; and in general there is in both a copious discharge of the previously retained excretions.

Asthmatic persons are often subject to a slight habitual wheezing in some part of the chest, and also to an occasional cough, with or without slight expectoration, but with no other symptom of catarrh. These symptoms have been described to me as occurring on exertion in the open air after prolonged rest; they are accompanied with slight dyspnoea, and this, together with the rest of the symptoms, ceases when the exertion is continued long enough to produce some degree of re-action. These phenomena are unquestionably the minor degree of the paroxysm; they are probably caused by the same irregular action of the bronchial muscles as causes the latter, but do not reach the climax, because the nervous centres are awake to the first approaches of disorder, and the excitement and quickened respiration consequent on exertion produce the cure. The aggravated asthmatic paroxysm always occurs during sleep, when the energy of the nervous system is at the lowest, and the comparatively quiescent condition of the respiratory function favours the accumulation of mucus. It seems probable that the asthmatic paroxysm is attended with more or less of pulmonary collapse, the consequence of the accumulation in the bronchi; but I have not had an opportunity of direct observation on this point. It is certain, however, that this accumulation must seriously contribute to the production of the most distressing symptoms of the paroxysm. The spontaneous cure in the real paroxysm, as in the minor attack, or threatening of asthma, above referred to, usually takes place when the nervous centres have been thoroughly roused, and the whole system brought into a state of reaction by the exertion consequent on the dyspnoea.

An interesting fact, in connection with asthma and other spasmodic respiratory diseases, is the frequent occurrence of vomiting during the paroxysms, a fact which points to the probable dependence of all these affections on some morbid condition in the communication of which the pneumogastric nerve and the medulla oblongata are the principal parts concerned. A phenomenon exactly the converse of that just alluded to, is the profuse and immediate expectoration in cases of obstructive bronchitis after the administration of an emetic. Now it is interesting to observe, in relation to both these facts, and their bearing on the subject we have been considering, that Volkmann has apparently succeeded in demonstrating the influence of

stimuli applied to the trunk of the vagus nerve upon the muscular contraction of the bronchi,-a point left open to doubt, both by the experiments of Williams and by the subsequent ones of Longet.1 The expeditious and complete relief afforded by an emetic in cases in which there has been extreme difficulty of expectoration, is one of the most striking phenomena connected with bronchitis; and one of which, I believe, no sufficient explanation has yet been afforded. It appears, however, to be completely in harmony with the theory I have advanced in the preceding pages.

2

Another fact tending still further to illustrate this view, is found in the experiments of Reid, Longet, Schiff, and others, on the effects of section of the pneumogastric trunk, or of its visceral branches, on the lungs and bronchi. All experiments concur in proving that these operations are followed by a very large accumulation of frothy mucus in the bronchi. Changes in the lungs have also been observed, which seem to be of the nature of congestion and collapse, but are imperfectly described. M. Longet has also found emphysema of the lungs, the relations of which to pulmonary collapse will in these cases hereafter be considered; and there can be little doubt that we have all the phenomena of bronchial obstruction and collapse following the division of the nerve which, according to the views above proposed, is the chief regulator or excitor of the bronchial de-obstruent function.

To sum up the results of this discussion, as respects bronchitis, I would recapitulate the following points, which, if not established, seem to be at least rendered highly probable. Firstly, That pulmonary collapse from bronchitis, when recent and uncomplicated, appears to be susceptible of cure, on removal of the bronchial obstructions. Secondly, That this is usually effected, not so much by the agency of respiration, as by the muscular contractions of the obstructed bronchi themselves. Thirdly, That the derangement or paralysis of this de-obstruent function becomes a cause of bronchial accumulation even in the normal state of the mucous membrane, and, a fortiori, in cases of bronchitis. Fourthly, That the de-obstruent function of the bronchial tubes may be impaired by various causes acting on the pneumogastric nerve, either directly or through the nervous centres. And Fifthly, that it may be stimulated by remedies or other agents acting in a similar manner.

The application of these principles to pathology might be almost indefinitely expanded, if it were desirable at the present stage of the

1 Volkmann introduces into the trachea of a decapitated animal a tube having its outer end tapering and perforated by a rather small opening. This being placed opposite a flame, he isolates and galvanises the vagus nerve, when, at every application of the stimulus, the flame is observed to be blown aside.-Wagner's Handwörterbuch der Physiologie, vol. ii., p. 586.

2 Edin. Med. and Surg. Journal, April 1839; or Reid's Anatomical and Physiological Commentaries. Monthly Retrospect, 1849, p. 3. Longet-Systeme Nerveux.

inquiry to indulge in much farther speculation. But enough has probably been brought before the reader to show that the symptoms, causes, and cure of bronchitis and other allied affections, even when not resulting in demonstrable or organic disease, are illustrated by a clear conception of the phenomena of pulmonary collapse and its attendant conditions.

I now proceed to the consideration of some permanent disorganisations, for the most part well known to anatomists.

Permanent Lesions of the Air-Vesicles and Bronchi depending on Bronchitis.-Those which are enumerated by authors, and which I have myself seen, may be described as being principally of two kinds, -viz., permanent obliteration or constriction of these parts, and permanent abnormal dilatation of them.

The obliteration of the air-vesicles, leading to atrophy of the lung, has been viewed as a consequence of bronchitis by Dr Stokes, and in this respect he stands almost alone among the authors who have treated of this disease. In his work on "Diseases of the Chest," he says:" Atrophy of the lung has been recognised in a variety of diseases, such as tubercle, pneumonia, cancer, and pleurisy; but its direct connection with bronchitis has not been sufficiently examined." -P. 203. Dr Stokes argues for the possibility of this connection, on the ground, that "it is easy to see that when the air-tubes are obstructed, the cells to which they lead will diminish in volume." He gives, however, no experience of his own upon the subject; and in speaking of emphysema, he adopts Laennec's opinion of its origin, which ascribes an entirely opposite result to obstruction of the airtubes. The views of Dr Stokes upon this subject cannot, therefore, be considered as very clear or consistent, though I believe the merit of suggesting that atrophy of the lung may depend on bronchitis, belongs, in the first instance, to him.

Dilatation of the air-cells, or emphysema of the lung, a condition mentioned by Sir J. Floyer, Morgagni, Baillie, and others, was first accurately described by Laennec, and was by him considered as a consequence of bronchitis. Almost all pathological writers since Laennec's time have concurred with him in this opinion, with the exception of M. Louis, who, on grounds which will be hereafter noticed, has cast a doubt over the alleged production of emphysema by catarrh, while admitting their frequent co-existence. I have already alluded to some points in which Laennec's view of the connection of these two affections is open to attack; but the correctness of his observation, as to the dependence of emphysema in many cases on bronchitis, is, I think, quite unquestionable, notwithstanding the arguments of M. Louis. This will, I hope, appear clear from the sequel.

Along with this affection may be placed the "interlobular emphysema" of Laennec, which is produced under nearly the same circumstances, and often simultaneously with the dilatation of the air-vesicles. It is, however, an essentially different affection, not only in

I

its site, anatomical character, and mode of production, but also in its result, inasmuch as it is never, I believe, a truly permanent lesion, and would, therefore, have been more correctly, though not so conveniently, noticed in the former part of this memoir.

Obliteration of the Bronchi is somewhat slightly and confusedly alluded to by Andral as a consequence of bronchitis, having been altogether passed over by Laennec. It is treated anatomically as an independent affection by Reynaud at great length;1 and the conclusions of Reynaud's memoir have been elaborately adapted to the subject of bronchitis by Dr Stokes. With these exceptions, the obliteration of the bronchi has received, like the atrophy of the lung, but little attention, except as a sequel of tuberculous and other primary diseases of the lung itself.

It is very different with the opposed condition of the dilatation of the bronchi, which, since its elaborate description by Laennec, has been almost universally admitted by pathological writers to be connected with, and probably caused by, bronchitis, although the nature and origin of the affection have led to much difference of opinion, and are still among the obscurest points of pulmonary pathology.

In addition to these lesions, I have likewise to include, as a consequence of bronchitis, the pulmonary concretions which are frequently found in the midst of atrophied and indurated portions of pulmonary tissue, and which have been described by Bonetus, Morgagni, and almost all the earlier pathological anatomists, as often connected with asthma. It is well known that the tendency of modern opinion has been to follow Laennec in considering these bodies as the result of cured tubercle,-a view of their origin which, though undoubtedly correct in many cases, I am induced to regard as too exclusive, and as therefore requiring modification.

Upon the anatomy of these affections I shall have so much to say in my next paper, as may serve to illustrate their relation to one another, and to the primary results of bronchitis already described. I propose, however, to treat chiefly of the causes and mechanism of their production,—a pathological difficulty to which the knowledge of pulmonary collapse, as a frequent result of bronchitis, furnishes, I believe, the sole and indispensable key. Those who are acquainted with the confusing and apparently almost hopeless discordance of opinion on most of these subjects, among both practical and systematic writers, will not look upon any attempt at their reconciliation as a superfluous task.

For the convenience of the printer, I insert here a table of cases of emphysema of the lung, to which reference will be made in next Number.

1 Memoires de l'Acad. de Méd., T. iv.

TABLE OF FORTY CASES OF PULMONARY EMPHYSEMA, SHOWING ITS CONNECTION WITH OTHER AFFECTIONS, ESPECIALLY OF THE LUNGS.

Condensation, non-granular at posterior None mentioned.
portion of R. L. Lobular condensation.
Cretaceous tubercle in apices.

Cholera. No detail

ed history of symp-
toms. Died in re-
action, with consi-
derable dyspnoea.