particle of air finds its way into the interlobular partitions; nay, that these partitions may themselves be lacerated, and yet no interlobular emphysema be produced. Farther observations are required to elucidate this subject.

This form of emphysema is as rare as the other is common. It is very seldom combined with the true pulmonary emphysema; and in the great majority of cases seems to result from some sudden and violent effort of the respiratory muscles, as in the forcing pains of child-birth, in raising heavy weights, in hooping-cough, &c. Notwithstanding the greater density of their lungs, children appear to be more liable to this disease than adults.*

The only symptom from which the existence of this disease can be suspected, is the sudden supervention of dyspnea after any violent effort of the lungs. Its stethoscopic signs are the dry crepitous râle with large bubbles, and the friction of ascent and descent already described. These sounds, it will be recollected, are likewise common to the vesicular form of emphysema when the pleura is projected by several air-cells thrown into one; perhaps the only method of distinguishing between these cases is by the sudden supervention of the dyspnoea and of the stethoscopic signs in the interlobular form of the disease: fortunately, however, the diagnosis is not a matter of much practical importance, as in the slighter cases (in which alone any ambiguity can exist) the air appears to be always absorbed, and the interlobular partitions gradually return to their natural state. When the aerial infiltration extends to the external parts, the difficulty of diagnosis is at once removed, and the disease may be treated on the principles already stated in the preceding article on general emphysema.

(R. Townsend.)

EMPYEMA. Eμsinua, formed of iv and Tov, literally signifies an internal collection of pus, and in this general sense was employed by several ancient authors. By subsequent writers its signification has been considerably restricted, and nosologists now apply the term exclusively to those collections of pus which are contained within the sac of the pleura. In practice, however, it is not always easy to determine, a priori, the precise nature of the fluid collected within the chest, as its physical characters are found to vary considerably, even in those cases that most closely resemble each other in their origin, progress, and symptoms. In a case of empyema of two months' standing, occasioned by the bursting of a tuberculous abscess of the lung into the pleura, the effusion, as observed by the writer, presented all the characters of genuine pus; while in another case, where the pleuritic effusion was produced by a similar cause, and assumed the same chronic form, the operation of paracentesis gave issue to a fluid as transparent and colourless as water.

Laennec.

Other varieties, to be presently enumerated, have likewise been observed in the appearance and composition of these fluids; and as there are no peculiar symptoms by which we can always discriminate their precise nature during the lifetime of the individual, the term is now generally used without any reference to the puriform character of the effusion.

When effusion into the thorax takes place in an individual of a dropsical diathesis, and seems to result from an obstruction to the circulation and the consequent transudation of the serous part of the blood, rather than from any irritation of the secreting surface, the disease is denominated hydrothorax. When the effusion is known to consist of blood, as in penetrating wounds of the chest, where the pulmonary or intercostal vessels have been injured, the term hæmothorax is used to express it; and the name of pneumothorax is applied when the effusion is of a gaseous nature. With these exceptions, all cases of effusion into the pleura that are sufficient to compress the lung and impede the function of respiration, are comprehended under the generic appellation of empyema.

The pleura, like other serous membranes, constantly exhales a fluid, in the form of va pour, by which its surface is lubricated and moistened. In the natural state, this perspi ratory fluid always exists in the form of halitus or vapour; but in a morbid state, it is sometimes exhaled in much larger quantities, and instead of vapour assumes the fluid form. Its qualities are then also materially altered, so that, instead of a slight moisture barely sufficient to facilitate the gliding motion of the opposing surfaces on each other, the serous sac is filled with certain morbid secretions, of which the following are the principal

1. Serum its composition is sometimes the same as that of the blood, and sometimes differs from it in containing a greater or less proportion of albumen.

2. The same combined with a certain quantity of the colouring matter of the blood. 3. Pure blood.

4. Pus.

Andral, Anatomie Pathologique.

Chroniques, Clinique Médicale,) contain the most complete history we possess of these diseases, and may indeed be said to form a new era in the pathology of this class of affections.

The effusion of empyema, it is now generally admitted, is in all cases principally, if not entirely, formed by a morbid secretion from the pleura, and may in almost every instance be referred to inflammation of that membrane, either in an acute or chronic, an evident or latent form; and even in those cases where pus or other matter is introduced into the pleura from an extrinsic source, as from the rupture of a pulmonary or hepatic abscess, the collection of fluid which constitutes the empyema consequent thereon, does not consist so much of the matter of the abscess as of the morbid secretion from the pleura which the irritation caused by the presence of that matter produces.

The nature of the exudation in acute pleuritis, and the successive stages of its organization and conversion into false membrane, are detailed in a separate article in this work. (See PLEURITIs.) For our present purpose, it is only necessary to consider those morbid secretions of the pleura which evince no disposition to become organized or absorbed, but continue to accumulate in the shut sac of that membrane, where they act as a foreign body, and, by their pressure on the important organs contained within the parietes of the chest, present a constant obstacle to the due performance of their functions.

In some cases the effusion consists of a clear, transparent, or lemon-coloured serum; sometimes the effused fluid, though it still retains its transparency, contains several flocculi of albumen, some suspended and others precipitated to the bottom. More frequently it is rendered quite turbid by the quantity of these minute flocculi that are partially dissolved and suspended in it, while the pleura, more especially the most dependent portion of it, is covered with an inorganic layer of a white or yellowish paste formed by these flocculi, which fall in the form of a sediment to the bottom of the fluid in which they were suspended. In other cases, and they are by far the most numerous, the effusion is still more turbid, and of a greyish brown or yellow colour-in short, it exhibits every intermediate variety of appearance until it presents all the characters of genuine pus.

These different varieties of effusion are sometimes mixed up with the contents of abscesses formed in the neighbouring parts, as in the lungs or liver, and discharged into the pleura. In some cases the effusion is coloured by the admixture of a certain quantity of blood, and in some rare instances the effusion has been found to consist entirely of blood. This sanguinolent effusion sometimes occurs at the very onset of the pleuritic attack, constituting the primitive hemorrhagic pleurisy of M. Laennec, but is more frequently observed to occur at a more advanced stage of pleurisy, particularly at the time when vessels begin to be formed in the false membranes,

or when a fresh attack of inflammation supervenes in them. Much importance was attached by the older writers to the decomposition of these effusions and their tendency to putrescency; but the best pathologists are now agreed that they never acquire an offensive odour, or exhibit any sign of decomposition unless when the parietes which enclose them become gangrenous, or when a communication has been established between the fluid and the external atmosphere.*

The quantity of these effusions is sometimes so very great as to compress the lung into the smallest possible compass, and exhaust it of its air more effectually than could be done after death by means of an air-pump; at the same time the parietes of the chest which are in any degree susceptible of motion are distended to the utmost; the ribs are elevated, and their lower margins everted, so as to increase their capacity as much as possible; the intercostal spaces are protruded; the diaphragm is forced down into the abdomen, and the abdominal viscera are consequently displaced, especially the liver, which, in cases of extensive empyema of the right side, has been known to descend into the iliac fossa. The mediastinum, in like manner, yields to the distending force of the effused fluid, compresses the opposite, lung, and allows the heart to be thrust completely out of its natural situation. We shall presently see that this displacement of the heart is one of the most constant and least fallible symptoms of empyema. Without this great enlargement of the affected side, it would be physically impossible that one sac of the pleura could accommodate such an enormous quantity of fluid as has occasionally been found there.

A patient of Dr. Croker, of Dublin, was lately operated on for empyema by Mr. Crampton, when the almost incredible quantity of fourteen imperial pints of pus was drawn off from the left pleura. In Dr. Archer's case of successful paracentesis of the thorax, recorded in the second volume of the Transactions of the Dublin Association, eleven pints of an inodorous fluid were drawn off, and in a few weeks after the patient was quite convalescent. Many other instances might be quoted of effusions equally great, or even still more extensive.

When the effusion is removed, it seldom happens that the pleura is exposed to view, as its surface is almost invariably covered with a coating of adventitious matter, which gives the interior of the chest much more the appearance of the walls of a large abscess than of a cavity lined with serous membrane. When, as in cases of latent pleurisy, the pleura is covered with a layer of the inorganic sediment, which is deposited when the effusion is wholly puriform, the layer of matter may be scraped off with the handle of the scalpel, and then the membrane underneath presents

Andral and Broussais, Op. Cit. Stoll, Ratio Medendi.

an opaque blueish appearance, as if caused by the maceration to which it had been so long submitted. A few red dots or striæ, as if laid on with a pencil, are generally dispersed over its surface; the membrane itself is seldom if ever really thickened, its apparent thickening being in almost every instance caused by a coating of adventitious membrane, which had been exuded during the earlier stages of the inflammation. When the chronic pleurisy succeeds to an acute attack, this apparent thickening of the pleura is a very constant appearance: sometimes the adventitious membrane forms a delicate transparent pellicle which appears perfectly incorporated with the subjacent membrane, but may however be dissected from it in one or more layers; sometimes the pleura is closely studded with minute transparent or opaque granulations of a flattened form, but most frequently the adventitious coating is of an opaque whitish colour, and varies in consistence from curd or soft cheese to fibro-cartilage, to which substances it often bears a very strong resemblance; and as it is generally composed of several strata laid one over the other, it sometimes forms a dense solid layer many lines or even inches in thickness. When a coating of this description is developed on the pulmonary pleura, it forms such an unyielding envelope round the lung in its compressed, contracted state, as must effectually prevent its expansion when the pressure of the fluid is removed; and as the lung in this condition cannot dilate itself promptly enough to keep pace with the progress of absorption, when the disease terminates favourably, the parietes of the chest must necessarily fall in to occupy the space left by the removal of the fluid in this way is produced the contraction of the chest which so constantly follows the removal of a chronic effusion from the pleura either by absorption or evacuation.

The adventitious membranes which line the pleura are liable to a variety of morbid alterations; they are evidently susceptible of inflammation, and likewise of ulceration; for in many cases they have been observed eroded, as it were, with small circular pits, sometimes shallow and sometimes penetrating through the whole thickness of the false membrane : occasionally these penetrating pits communicate with each other by sinuses, or by a more extensive separation of the false membrane from the subjacent pleura, but at other times the ulceration penetrates through the pleura itself. When this happens on the costal pleura, it sometimes gives rise to the formation of external tumours, which either burst externally and discharge the matter of the empyema, or else form one or more sinuous passages by which the pus is infiltrated into the subcutaneous and intermuscular cellular tissue; but when it takes place in the pulmonary pleura, a communication is eventually formed with a bronchial tube, through which (according to the position of the body at the time) part of the fluid escapes, or air enters. Several cases illustrative of these morbid appearances

are recorded in Dr. Duncan's interesting essay on empyema and pneumothorax in the 28th volume of the Edinburgh Medical Journal. The pleura and its adventitious coating of false membranes is likewise subject to gangrene, and the detachment of the gangrenous eschars sometimes serve, as in the case of simple erosion just noticed, to form an outlet by which the matter of the empyema is evacuated.

These false membranes are likewise liable to other morbid changes. Sometimes they are transformed into fibrous or cartilaginous tissue, and in some instances they have been found completely ossified; they are also liable to the development of various morbid productions, particularly tubercle. The tubercles that are formed in false membranes are generally small and very numerous. We have, however, once or twice seen tubercles as large as filberts, in the adventitious coating of the pleura; their development is usually a slow process, and generally occurs in cases of very chronic pleuritis; but sometimes they are generated in great numbers with an extraordinary rapidity. M. Andral has seen the false membranes studded with tubercles in persons who died of acute pleuritis of only fifteen days standing.*

The morbid alterations which we have described may exist in both sacs of the pleura at the same time, constituting the double empyema of authors, or, as much more commonly happens, may occupy one side of the chest; or, lastly, may be limited to a part of one side. When the inflammation is limited to a certain extent of the pleura, the effusion is generally circumscribed by adhesions which prevent its creeping into the general sac of the pleura; these circumscribed empyemas, as they are termed, may exist between the lower lobe of the lung and the diaphragm, or between two contiguous lobes, between the inner surface of the lung and the mediastinum, or between any part of its outer surface and the costal pleura. Not unfrequently there exist between the pleura costalis and pulmonalis a number of dense firm adhesions, which, like so many shelves or partitions, intersect the effusion, and divide the sac of the pleura into a number of distinct compartments. We examined the body of a patient who died of empyema in the Whitworth Hospital, in March 1830, in whom the effusion was divided by these partitions into three compartments, so perfectly distinct from each other, that had the operation of paracentesis been performed during life that compartment only could have been evacuated into which the incision had been made; so that in order to draw off the entire effusion, it would have been necessary to perform three several operations.

The effect of the effusion in compressing the lung and diminishing its volume, has already been alluded to. When the effusion is very extensive, the lung becomes flattened and

• Clinique Médicale, vol. ii.

completely flaccid, and its surface corrugated like the shrivelled rind of a withered apple; in this state the pulmonary tissue is soft, pliant, and dense, like a piece of skin, without any crepitation, more pale than natural, and almost entirely without blood; its bloodvessels are flattened and frequently appear quite empty. The lung thus circumstanced is incapable of expanding for the admission of air so long as the fluid continues to press on its surface: its alveolar texture, however, continues very distinct; and, when its surface is not coated with an unyielding false membrane, it may be readily restored to its full dimensions by inflation. The usual position which the lung thus compressed occupies, is by the side of the spinal column, against which it sometimes lies so close as to have escaped the observation of several distinguished anatomists, who accordingly described it as totally destroyed by suppuration. Its position may, however, be materially altered by adhesions attaching it to different points of the thoracic parietes, and preventing its receding from them. We have known the lung retained in close contact with the whole anterior part of the chest, while the fluid was accumulated in the posterior part. Andral records a case of empyema, in which the upper and middle lobe of the right lung were retained in their natural position by adhesions, and formed a complete roof over the effusion, which filled the whole of the lower part of the chest.+ Drs. Graves and Stokes relate two remarkable cases of empyema in the fifth volume of the Dublin Hospital Reports, in both of which the lungs were attached from their apex to their basis by a vertical adhesion of about two inches in breadth. Other observations might be adduced illustrative of the effects of adhesions in preventing the lungs receding from the parietes of the thorax; but for our present purpose it is sufficient to remark that, as there is no part of the pulmonary pleura which may not contract adhesions with the corresponding surface of the costal pleura, so there is no part of the chest with which the lung may not be retained in contact, even in cases of very copious effusion. The knowledge of this anatomical fact is, as we shall presently see, of considerable importance in some cases for determining the presence of empyema, and likewise for selecting the site of the operation of paracentesis.

The lung, when compressed in the manner we have described in the preceding paragraph, is seldom attacked with inflammation; indeed its exanguious condition would seem to guarantee it sufficiently from attacks of that nature; but there is another morbid alteration which the lung under such circumstances frequently presents, namely, the development of tubercles. M. Broussais supposes that their formation is in most cases consequent to the effusion, and in a great degree, if not altogether, produced by the obstruction of the

Laennec, Op. Cit.

+ Clinique Médicale, vol. ii.

lymphatic circulation in the part.* A more general opinion however is, that tubercles are in this, as in other cases, the result of a general diathesis, and had probably existed in the lung before the effusion had taken place. M. Broussais's opinion, if correct, would furnish a strong argument in favour of operating at an early period of the effusion, in order to anticipate, if possible, the formation of the tubercles. Another morbid appearance which the lung occasionally presents is the formation of a gangrenous or phlegmonous abscess, by which, when the pleura is perforated, the effused fluid finds a passage into the bronchi, and is expectorated.

Such are the principal morbid appearances that have been observed after death in cases of empyema: it now remains for us to investigate the causes of these anatomical lesions, and to consider the symptoms to which they give rise, and by which they may be distinguished during life. We shall thus be prepared to form a correct estimate of the progress and termination of this disease, and of the remedies best calculated to arrest its progress and remove its effects.

We have already seen that the matter of empyema is in most cases formed exclusively by a morbid secretion from the pleura, and that, even in those instances where pus or other matter is introduced into the pleura from the rupture of an adjacent abscess, the empyema which follows is principally formed by exhalation from the inflamed pleura. It may, therefore, be assumed that inflammation of the pleura is the proximate cause of empyema. As, however, the ordinary course of pleuritic inflammation is not to terminate in empyema, but in the exudation of a compound fluid, the serous portion of which is subsequently absorbed, and the solid part organized and converted into false membrane, it becomes a question to determine what are the circumstances that cause the inflamed pleura to secrete the inorganic matter of empyema rather than the ordinary organizable product of pleurisy, or, in other words, what are the species of pleuritic inflammation which have the greatest tendency to terminate in empyema.

These may be divided into four classes: 1. Acute pleuritis of intense violence. 2. Acute pleuritis degenerating into the chro nic form.

3. Inflammation of the pleura of so low a type as not to present the ordinary symptoms of acute pleurisy.

4. Pleuritis caused by the introduction of foreign substances.

1. Acute pleuritis of intense violence.-It very rarely happens that inflammation of the pleura is so intensely violent as to induce gangrene. When it does occur, a copious effusion always follows. More frequently, when the pain and other inflammatory symptoms present an unusual degree of violence, blood is effused from the inflamed surface; generally speaking, the effusion of fluid is more abun

V Op. Cit. vol. i. p. 343.

dant in the hemorrhagic than in the simple pleurisy, and the tendency to absorption is much less. Lastly, when the pleuritis assumes this violent intractable character, a copious secretion of puriform matter may take place at an early stage of the disease. In a young woman who died in the Hardwicke Fever Hospital in the year 1826, after experiencing for twelve days before her death the symptoms of most violent inflammation of the pleura, we found, on dissection, nine pints of thick inodorous pus in the right pleural sac. M. Andral records another case in which a purulent effusion was formed with equal rapidity. Although the inflammatory symptoms were combated from the very outset of the disease by the most active treatment, on the fifth day the whole of the right side sounded dull on percussion, and respiration had ceased to be audible there; on the seventh, the side was evidently dilated; and on the eleventh, when the disease terminated fatally, the right side was found, on dissection, so filled with pus that the lung was completely condensed and flattened against the spine.f Piso likewise relates several cases of acute pleuritis, in which the patients died on the fifteenth, and some even so early as the ninth day, with their sides full of pus. In those acute cases of empyema, the diagnosis is never difficult; the extreme violence of the symptoms, the acute pain of the side rendered almost insupportable by coughing, the excessive dyspnoea, general anxiety, and high fever, at once point out the highly inflamed state of the pleura, and awaken our attention to the possibility of its terminating by effusion: when under such circumstances the physical signs of effusion (to be presently described) rapidly supervene, the existence of empyema is placed beyond a doubt. This acute form of empyema is, however, much more rare than those chronic forms of the disease we are next to consider.

2. Acute pleuritis degenerating into the chronic form. In the greater number of pleurisies which terminate favourably, the process of the absorption and organization of the effusion is completed within a limited period, which, at an average calculation, may be estimated at three weeks or thereabout. Whenever the symptoms of pleuritic inflammation outlast this period, or when, after a temporary abatement of the inflammatory symptoms, the patient is seized with rigors and irregular febrile paroxysms similar to those of remittent fever, there is reason to fear that the disease is about to assume the chronic form, and empyema may be apprehended. In many cases the passage of the disease from the acute into the chronic form may be traced to the circumstance of its having been neglected during its earlier stages, or not combated by sufficiently active treatment, or else to some indiscretion on the part of the patient during conva

Laennec, Op. Cit. Dr. Forbes's Translation.

+ Clinique Médicale, vol. ii. case 13. De Affect. a Seros. Colluv. ortis, sect. iii. cap. ix. Broussais, Op. Cit.

lescence, particularly in the article of diet; but we likewise meet occasionally with cases of acute pleurisy, which, however actively and judiciously treated, inevitably degenerate into the chronic form. M. Broussais, whose opportunities of observation in this matter have been most extensive, states, as the result of his experience, that acute pleurisy passing into the chronic form is decidedly the most frequent cause of empyema. Whenever, therefore, the symptoms of pleuritic inflammation outlast their ordinary period, and are succeeded by those of effusion, we have the strongest evidence of the existence of empyema, inasmuch as the symptoms of empyema make their appearance under those circumstances which most frequently lead to such a termination.

3. Inflammation of the pleura of so low a type as not to present the ordinary symptoms of acute pleurisy.-Several physicians of the last century, and particularly Stoll, had remarked that, in many cases of pleurisy, the stitch which commonly attracts attention to the character of the disease, is altogether wanting, and that the insidious mildness of the whole symptoms in the early stage is such as not even to excite any suspicion of a severe affection. This latent form of pleurisy is essentially chronic in its progress. At no period of its course does it present the intense fever, severe pain, or energetic reaction, which characterize an acute disease. It seldom occurs in persons of good constitution, but usually attacks those who have become cachectic from some cause or other, especially persons of a strumous habit. There are, however, certain exciting causes, which are said to have a peculiar tendency to generate this latent form of pleurisy, amongst which may be enumerated contusions of the chest, wounds of the pleura, the cold stage of ague, and metastasis of rheumatism. These causes, says M. Broussais,† most commonly give rise to pleurisies that are latent in their origin and chronic in their progress. Effusion of puriform matter may likewise take place into the pleura from other causes, and without being preceded by the ordinary symptoms of pleuritic inflammation. A case of latent empyema, consequent on venous inflammation, lately occurred in the Meath Hospital, under the care of Mr. Porter. The patient, a stout young man, in the course of a few days, after having been bled, was seized with symptoms of phlebitis, and diffuse inflammation of the cellular membrane extending along the arm to the axilla. disease proved fatal, and on dissection, in addition to the morbid appearances of the diseased limb, the pleura of the same side was found to contain several quarts of pus. this case, no symptom whatever was observed during life to excite any suspicion of the pleura being the seat of disease. We have also known the amputation for white swelling followed in two instances by copious depositions of pus in the pleura, and in neither

The

Laennec, Op. Cit. Dr. Forbes's Translation. + Op. Cit.

In