referred to. The continuance of secretion from the pleural surface for a greater or less period, and hence the constant renewal of empyema, is of very common occurrence. In rare instances, the characters of the newly secreted fluid remain those of that originally evacuated; in the great majority, they change, the general tendency of the change being to the purulent character. The alteration from the almost purely serous appearance to the purulent is sometimes accomplished in twenty-four hours. When the fluid has been originally more or less completely formed of pus, but of a laudable kind, its conversion into a purulent matter, of bad quality and fetid smell, is not unusually observed. Under these circumstances, the injection of warm water or some other unirritating fluid becomes advisable. Should there be much appearance of putrescency, a small quantity of very weak solution of chloride of sodium may be added. The notion of giving tone to, and diminishing the irritation of, the pleura, by injecting tonic preparations, seems of very questionable justness; nor has the practice been attended with sufficiently favourable results to warrant its general employment. Ioduretted solutions, or one of nitrate of silver, have more à priori reason in their favour.

In the ordinary course of things, when the case is destined to end by the patient's restoration to health, the wound or wounds in the thoracic walls gradually close, and cicatrization is perfect within a short period; but in some cases, the opening, instead of closing, acquires the characters of a fistula, which it retains for a variable period, and daily gives issue to more or less pus.

When spontaneous perforation of the costal pleura has occurred, and a portion of the contents of the pleural cavity escaped through this into the subcutaneous cellular membrane, forming an abscess there, this should be opened without delay, in order to prevent the occurrence of sinuses, and burrowing: so well established in this point, that the operation is under these circumstances termed empyema of necessity.

Cases of double empyema are, as a general rule, unfit for operation, unless evacuation be rendered necessary for the prevention of asphyxia. Should particular circumstances arise, under which paracentesis might on other grounds become admissible, an interval of time, varying in length with the condition of the patient, should be allowed to elapse between the two operations.

Varieties of Pleurisy.—The varieties of pleurisy are exceedingly numerous. The inflammation may be idiopathic or nonidiopathic,-in the latter case depending on some general disease (as typhoid or puerperal fever ;) on some diethetic morbid state, as Bright's disease; on some adjacent irritation, as that of pneumonia,* tubercle, carcinoma; on some traumatic cause; on perforation of the lung by tubercle, cancer, abscess, &c. Where necessary, the peculiarities of the inflammation, under these circumstances, will be noticed with the diseases causing them. In the present place, certain varieties of the idiopathic disease will alone be considered.

(a) Pleurisy is said to be latent, when it runs its course without producing decided subjective symptoms,-where there is neither local pain, cough, dyspnoea, nor febrile action. In cases of this kind, effusion may have reached to the clavicle, and driven the heart greatly out of its place, and yet the patient remain utterly unaware that his chest is the seat of disease. He seeks advice, either from a vague consciousness that he is not in his usual health, or for some ailment totally unconnected with the thorax. The physical signs reveal the true condition of things. The necessary treatment (once the disease is detected) is not modified in any important point (except that blood-letting need not be carried at all so far) by this latency of course; the great difficulty often consists in persuading the patient that there is really any thing of a serious character to treat. I have repeatedly known persons with copious effusion of this kind follow their usual, more or less laborious, occupations. (b) The portion of pleura inflamed may be very limited. The disease is then said to be circumscribed. When the phrenic surface is solely affected, the pain is more severe; orthopnoea is said to be frequent,-even with bending forwards of the trunk; the cough is more paroxysmal; there is hiccup, nausea, vomiting, delirium, excess of costal breathing, jaundice (if the disease be on the right side,) and, it is said, occasionally risus sardonicus.

Inflammation of the mediastinal pleura is often accompanied with serous infiltration of the cellular tissue of the mediastinum - itself; pseudo-rhonchus will then be heard along the sternum.

* A slight amount of plastic exudation in the pleura is so common in pneumonia that pleuro-pneumonia and pneumonia may, in that sense, be used as convertible terms; but pleurisy of clinical importance, and producing effusion, does not occur in more than about one-eighth of cases of pneumonia.

Pleuritic fluid accumulation, confined by adhesions between the lobes of a lung (inter-lobar pleurisy,) may simulate a solid mass in the pleura or in the lung itself, or an aneurism. Dull percussion sound, local bulging, weak or bronchial respiration, and intensified vocal resonance, may exist in all these cases. The pleuritic accumulation lies in the line of the inter-lobar fissure of the lung; the voice may have an ægophonic twang on its confines; there is no vocal fremitus over it; there is neither impulse nor murmur; and the affection has a past history different from the other diseases named. Similar local collections may form with a boundary of adhesions in any part of the pleural surface, and several such may co-exist, forming sacs perfectly independent of, or communicating with, each other, whence bilocular or multilocular empyema. The adhesions, forming the walls of these loculi, of course unite portions of lung-substance to the surface, and so give rise to various modifications in the physical signs. The general character of these modifications is, that wherever adhesions exist, blowing respiration is heard; and if a portion of lung, of any size (even though condensed,) be agglutinated to the surface, the percussion-sound will be clearer than directly over the fluid; the state of vocal resonance varies. I presume that on the right side the vocal fremitus would be retained over such portions of lung.

(c) Empyema, forcing its way through the costal pleura, may form one or more swellings under the skin, which rise and fall (if the parietal communication be free) with the acts of expiration and inspiration. This has long been known. But, some years since, Dr. M'Donnell showed, what had not previously been recognised, that a sub-cutaneous purulent collection of the kind may pulsate strongly and expansively, and hence simulate an aneurism. The absence of thrill and of abnormal murmur, the presence of the ordinary signs of empyema, and often the situation of the pulsatory prominence, will clear up the diagnosis. For fuller information, the valuable paper of Dr. M Donnell may be consulted.*

(d) But an empyema may become pulsatile under circumstances more singular than these, and still more likely to confuse the practitioner, I mean where there is no perforation of the costal pleura, and no accumulation of pus under the skin.

* Dublin Journ. of Med. Science, March, 1844.

*

I have twice, in cases presenting all the ordinary physical signs of empyema on the left side (with displacement of the heart to the right,) seen the inner part of the infra-clavicular and mammary regions close to the sternum, pulsate visibly, heavingly, and with the aorta, as proved by post-mortem examination, being of natural caliber. In both cases while the side generally was greatly dilated, gentle local bulging was manifest in the site of pulsation. The circumstances that determined the diagnosis in favour of pulsating empyema, were the absence of murmur at the seat of pulsation; the fact that the two sounds heard at this spot were very weak, and gradually increased in intensity, as the stethoscope was carried towards the heart; the absence of thrill below and above the clavicles, and of undue impulse in the latter situation; the perfect equality of the radial pulses; and the total absence of signs of concentric pressure. Taken singly, no one of these characters could be held conclusive, but the entire series formed a most serious body of evidence against the admission of aneurism. In both cases, the pulsation disappeared with the absorption of the fluid, and the return of the heart to its natural position: death arose from independent causes. Pulsation conveyed to empyema, and simulating aneurism by its force and heaving character, seems to be merely an excess of that slight fluctuation movement in the fluid which is far from uncommon in ordinary cases (p. 263.)

PNEUMONIA.

§ I.-Acute Pneumonia, or diffuse inflammation of the proper substance of the lung, is habitually divided into three stages: those of engorgement, of red hepatization, and of gray (or suppurative) hepatization. Dr. Stokes contends that a yet earlier anatomical stage than engorgement, marked by unnatural dryness of tissue and intense arterial injection, exists; and of the correctness of the opinion I, from actual observation, entertain no doubt.

I. Physical signs-Stage of arterial injection.-The respiratory murmurs reach the ear harsher, rougher, and sharper than natural from the affected part, provided this be near the surface; if the affected structure be deep-seated, on the contrary exaggerated respiration, from the intervening sound, but excited

The first of these cases was seen (April 3, 1843,) in consultation with Sir James Clark and Mr. Kingdom.

tissue, is heard. I have now seen a fair number of cases in which such exaggerated respiration, coupled with febrile excitement and slight pain in the side, were the earliest indications of a central pneumonia, eventually travelling to the surface. M. Grisolle holds that "in the great majority of cases, if not in all, weakness of respiration, often attended with loss of purity and of softness," marks the outset of the disease. Probably the fact is so, if the part actually inflamed be considered solely; but I have been unable to verify it. The same writer states, that he has, in a large proportion of cases, found weak respiration in the neighbourhood of already hepatized lung the precursor of signs of consolidation.

Stage of engorgement. The motions of expansion and of elevation are, if pleuritic pain be present, somewhat restrained; the vocal fremitus maintains its natural standard; the percussion-sound is more or less dull, according to the amount of engorgement; the respiratory murmurs are weak, suppressed, or masked by rhonchus in the affected parts, exaggerated in those at some distance from them and in the opposite lung; the vocal resonance is somewhat intensified, and slightly sniffling in quality. All this is accompanied with the rhonchus pathognomonic of this stage, the true primary crepitant.

Stage of red hepatization. Whether pure hepatization be capable of producing general expansion of the affected side, has been a theme of constant dispute. M. Woillez, maintaining the negative, justifies his opinion by a reference to the physical relations of the lung to its containing cavity, corroborated by the results of direct mensuration in two cases; in neither of these instances was the least degree of expansion detected. M. Grisolle obtained similar results from circular and antero-posterior admeasurement in four cases; nevertheless, he believes, upon the evidence of two others, that the inflamed lung may, quite independently of pleuritic effusion, determine "general or partial dilatation." In one of these, slight bulging of the infra-clavicular region (the disease occupied the upper lobe, and especially its anterior part) was detected on the patient's admission, the third day of the affection. This bulging having gradually increased with the progress of hepatization, M. Grisolle considers himself justified in referring its appearance to the inflammation of the lung; the post-mortem examination proved the absence of pleuritic effusion. In the other instance, bulging of the