coughing, and perhaps, in part, by the pressure of a large quantity of mucus within the tubes. At any rate, it is found to exist in connection with a copious secretion, which is not readily expectorated.

Dilatation of the bronchi has several modifications of form. Sometimes a single bronchus, or several ramifications of bronchi, become rather uniformly enlarged throughout; or the branches may even be larger than the principal trunk affected. In this case, a tube, which, while of a normal size, would only admit a common probe, will sometimes become large enough to receive a goose-quill, or even a person's finger. Accompanying this dilatation, it is proper to remark, the mucous membrane of the enlarged tubes becomes thickened by the existing inflammation or its effects, and loses its transparency. In another variety of dilatation, the enlargement exists in a single spot, so as to form a cavity at that spot. This cavity is sometimes of the size of a chestnut. In this case, as in the first, the mucous membrane is generally thickened. A third variety consists in there being a series of such cavities. In this case, the coats are sometimes thin, the dilatation being the result of weakness and pressure, not accompanied with or preceded by much active inflammation. As the consequence, the disease is attended with more debility than the other varieties; and almost any increase of respiration produces dyspnoea.

Generally, in the different cases, there is, to a greater or less extent, a condensation of pulmonary tissue around the dilated bronchi. This is caused by a deposit of new matter, essentially in the same way as all granulation structures are formed. It is usually regarded, however, as more albuminous or less highly organized, than are ordinary deposits on serous membranes. It is more like the secretion from the mucous membrane of the trachea in croup.

The other class of lesions to which the bronchi are subject, and to which I have referred, consists of cases in which the walls of the tubes become thickened and the caliber diminished. In these cases, if there is a secretion, it is essentially the same as that of croup. It is the result of active preceding inflammation, not attended by the violence which produces enlargement. The

albuminous deposit may completely obliterate the canal of a tube; and when it does, it is sometimes called a bronchial polypus. The tubal cavity, however, may be blocked up, by simple inflammation, which, for the time being, thickens the walls. In the former case, the obstruction is permanent, unless removed by ulceration or absorption, as is the deposit in pneumonitis. In the latter case, the difficulty vanishes with the subsidence of the inflammation.

DIAGNOSIS.-In that variety of dilatation in which the enlargement extends equally throughout a tube or tubes, the air does not so reverberate as to give cavernous respiration. Of course, the sound is only the shrill bronchial; and the character is rendered full and marked, in proportion to the degree of inflammation and induration in and around the tubes. When the enlarged tubes are loaded with mucus, we have, of course, the mucous rale; or, in case some of the smaller tubes are enlarged to those of medium size only, we then have in them the sub-crepitant rale. The respiration being the shrill bronchial, the sound of the voice, heard over the enlarged tubes, will be that of bronchophony.

In the second variety, and in the third, we have distinct cavernous respiration and pectoriloquy; inasmuch as a cavity and cavities, in these cases, are distinctly formed. Or when these cavities are loaded with mucus, we necessarily have the gurgling rale.

In all cases, in which there is appreciable induration of the pulmonary tissue around the dilated tubes, we, of course, have dullness on percussion, much the same as in pneumonitis.'

The discrimination of this lesion from pneumonitis is generally easy. In pneumonitis, the progress of the disease soon changes the character of the sounds heard. In dilatation of the tubes, they remain longer unchanged. In phthisis, sometimes the symptoms of the disease are more nearly like those of dilatation. In phthisis, generally the cough, the fever, the emaciation, and other symptoms will sufficiently characterize the disease; whereas, in dilatation of the tubes simulating tuberculous cavities, there are generally marked evidences of the existence merely of bronchitis. Chronic bronchitis, however, dilatation of tubes, and

tubercles in the lungs may all exist simultaneously, and so render the diagnosis obscure. When the dilated tubes are in the supeperior lobe of a lung, the tissue of that lung may break down and form a tuberculous cavity, thus bringing the two kinds of cavities into juxtaposition, or uniting both in one.

In the second class of lesions, the prominent auscultatory sign is a diminution or almost a cessation of the respiratory sound, over the affected part, the effect, of course, being proportioned to the degree of obstruction in the tubes. The bronchial cavity may be even entirely obliterated in some parts, and then the respiration in those parts will be entirely wanting. When the obstruction is from inflammation and not from a deposit of albuminous matter, the absence of the respiratory sound is of short duration. If a collection of mucus assists the inflammation in producing the obstruction, the simple act of coughing may partially restore the sound of respiration. When there actually is an adventitious deposit, the absence of the respiratory sound will, of course, continue permanently, or till that deposit is removed by ulceration or absorption.

The prognosis generally, in cases of morbid changes in the bronchi, is often favorable. Often a partial or an entire cure may be wrought, and, where it cannot, but the lesion continues unabated, still, if not complicated with a more serious affection, it seldom hastens very greatly the termination of life. It weakens the vital powers, but does not immediately arrest their action.

TREATMENT. The treatment to be adopted in the cure of morbid changes in the bronchi is not extensive nor difficult. But little comparatively can be accomplished, directly, by any remedial means. The object to be mainly aimed at, is to remove any existing bronchitis or other attending affection, and to strengthen the powers of vitality, that, as far as possible, they may restore the parts to their normal condition.

CHAPTER V.

PNEUMONITIS.

The term pneumonitis is formed from the Greek word, avsuμwv, signifying a lung, by appending itis, the usual termination to indicate inflammation. Pneumonia, it is true, is the orthography more commonly adopted; but, as this is not analogical, I reject it.

Like bronchitis, pneumonitis is ordinarily an acute and primary disease, but has, at the same time, several modifications of form, which require special consideration. Its mode of existence differs from that of bronchitis in one important respect-it never assumes a form so distinctly chronic as that which is sometimes taken by bronchitis. In illustrating the disease, I prefer, for brevity's sake, to describe its usual characteristics under the unqualified designation of pneumonitis.

SECTION I.

PNEUMONITIS.

PATHOLOGY.-This disease is generally said to consist in inflammation of the areolar tissue of the lungs. But shall we use the terms parenchyma and areolar tissue as synonymous, and say that the inflammation is limited to that tissue? To answer this question understandingly, we must first attend to a few considerations in the anatomical structure of the lungs.

The ultimate ramifications of the bronchi terminate in vesicles, which are arranged in lobules, the vesicles of each lobule communicating with one another, but not with those of other lobules. Each lobule is supplied with capillary blood-vessels, which surround and line the vesicles with a minute and intricate plexus, so arranged as to form the parietes of contiguous cells, and thereby favor the aeration of the contained blood, by exposing it, on both sides, to the contact of the contained air. These bronchi, vesicles, and blood-vessels, together with lymphatics and nerves which accompany them, are bound together by strong

areolar tissue; and every portion whose vesicles are involuted as described, constitutes a lobule. Since, now the term parenchyma is used to express the substance of the lungs, it may, with propriety, be extended so as to embrace not merely the areolar tissue, but all these tissues united, so far as they are contained in and constitute lobules,-particularly the areolar tissue, the bloodvessels, the vesicles, and the extremities of the bronchi terminating in the vesicles.

The older pathologists have discussed the question, whether pneumonitis is really inflammation of the areolar tissue or only of the vesicles; but, in view of the anatomy of the parts as just described, and in the light which is now thrown on the nature of inflammation, it cannot for a moment be doubted that, in this disease, all the tissues in the lobules are involuted. Indeed, post mortem examinations have set the matter at rest ;-it is so. Bronchitis is inflammation of the mucous or lining membrane of the tubes, whether that inflammation extends to the extremities of the tubes or not. Pneumonitis is inflammation extending throughout the substance of the lung embracing every thing but the pleura, which is the external lining.

Pneumonitis may commence in either of two ways. It may have its origin in bronchitis, the inflammation on the mucous tissue of the bronchi, passing down to the vesicles and thence involving the other tissues; or it may commence directly in the tissues constituting the vesicular structure, and extend to the surface of the lung, there implicating the pleura, and constituting pleuro-pneumonitis. The pleura may even be the part primarily inflamed; and, from this, the inflammation may extend inward upon the parenchyma. When, in such a case, the evidences of inflammation of the pleura are more marked than those of inflam mation of the parenchyma of the lungs, the term pneumo-pleuritis has sometimes been employed to designate the disease, it being then intended to restrict the pleuro-pneumonitis or pleuro-pneumonia to those cases in which the pulmonary parenchyma is most affected.

Unlike bronchitis, pneumonitis is, almost always, attended with considerable constitutional disturbance. The reason of the dif ference is obvious. In bronchitis, the bronchial tubes are open,