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the most common is softening. The softening begins usually in the centre of the mass, whether that be large or small, and a communication being established with a bronchial tube, the softened matter is expelled, and a cavity results. The masses situated nearest to the apex are commonly the earliest to liquify, but not always. Sometimes general softening appears to attack all the solidified patches of tissue, and the lung is then found to be riddled with abscesses which communicate with one another.

The cavities vary in size, according to the size of the mass which has undergone liquifaction. The smallest are about the size of a pea; the largest may be as big as an orange. If small, they are usually numerous : if large, the number is less. Sometimes a large cavity is seen, surrounded by smaller ones which communicate with it. If the cavity is situated in the interior of the lung, it is surrounded by solidified and softened tissue. If on the surface, it is covered on one side by the pleura, and unless adhesion takes place between the opposed surfaces of the pleura, perforation readily results. Stretching across the hollow of the cavity are often seen slender bridges of lungtissue, containing blood-vessels obliterated or still permeable. This is a condition much more common in the child than in the adult.

A lining membrane is usually described as belonging to cavities in the lung. Dr. Andrew Clark, however, believes this view to be incorrect. The wall consists of the ordinary tissue of the lung, loaded with tubercular or other matters. Of this diseased tissue, the innermost layer is in a state of disintegration, and can sometimes, although not always, be stripped off: hence the idea of its being a lining membrane. The secretion he believes not to be a real secretion, but to consist of the softened part of the disintegrated layer, which, becoming liquid, is expectorated. New infiltration goes on at the circumference of the wall of the cavity, and continued disintegration, producing more and more of the so-callel

secretion, on the inner side. If the infiltration is greater proportionately than the disintegration, the cavity becomes smaller, and may even almost close. If the disintegration is greater than the infiltration, the cavity extends.

It is the larger masses in the lung which are especially prone to disintegrate and soften down: the consolidation resulting from scrofulous pneumonia seems always to undergo this change. In the case of the grey and yellow granulations other alterations may take place. They may become inspissated by absorption of their watery parts, and remain as little opaque, greyish, hard lumps. This is not an uncommon change in the grey granulation. Or they may become cretaceous, being converted into small, dry, white masses, like bits of chalk. These two changes are equivalent to a cure; but although the local effects of the disease are thus rendered harmless, the disease itself may still continue, and new grey granulations may be seen surrounding cretaceous masses, showing that in spite of the local effort at repair the influence of the tubercular diathesis had remained as powerful as before. Even cavities sometimes, although rarely, close and cicatrize. In such cases, a fibrous nodule is found in the site of the cavity. It is usually small, of a whitish-grey colour, and has often fibrous bands radiating from it into the healthy tissue. The small bronchi are seen to end abruptly at the cicatrix, showing where they had been cut off by the ulcerating process at the time of formation of the cavity. The existence of the cicatrix is indicated, if it be near the surface, by puckering of the pleura over it.

Besides the pathological alterations which have been described, there is another variety of pulmonary phthisis, which is found in children as well as in adults. This is a form of cirrhosis, and is the condition to which, under the name of fibroid phthisis,* attention has been lately directed

* Report on a Case of Fibroid Phthisis, by Dr. Andrew Clark, read before the Clinical Society, Feb. 14, 1868.

by Dr. Andrew Clark. The whole lung is diminished in size, and is adherent to the pleura. A certain portionusually the lower part becomes shrunken, dense, and slatecoloured. On examination, fibrous septa are seen passing in different directions through the diseased part: some horizontally, which seem to consist of obliterated vessels and bronchi thickened by adventitious fibroid tissue; others intersecting, which consist of true areolar tissue, and occupy the interlobular spaces, ramifying in varying directions from them. These septa enclose portions of lung which contain yellow cheesy matter in a state of disintegration, or are broken up into cavities. The bronchial tubes are here and there dilated. In the very dense part of the lung the alveoli were found in several cases by Dr. Andrew Clark to be filled with "what seemed an amorphous substance, having occasionally an appearance of fibrillation."

This condition of the lung may be complicated with true grey or yellow tubercle. It is often, however, a distinct disease, and may thus be only a part of a general disorder, the same fibroid changes going on in other organs, as the kidney, liver, spleen, &c.

Diagnosis. The diagnosis of pulmonary phthisis is difficult or easy according to the amount of disease, the stage which has been reached, and the exact pathological condition which gives rise to the symptoms. We can readily detect consolidation, and can often determine the exact structural change to which consolidation is principally owing; but whether or not it is entirely due to this cause -whether other structural alterations may not be present to complicate the case—is frequently a question of the greatest difficulty to determine.

In all cases the great point to decide is the presence or absence of tubercle, for that may exist alone, or may accompany the other pathological conditions of the lung which have been described.

When tubercle exists alone, disseminated through the

lungs, it is often, owing to the obscurity of the physical signs, impossible at the first, or even after several successive examinations, to come to any positive conclusion as to the exact nature of the disease. To arrive at a diagnosis we must take into account the family history, the special history, the conformation of body, and especially the course of the physical signs. Thus, if a child, born of consumptive parents, and whose general build corresponds to the type which has been described as significant of the tuberculous diathesis, becomes languid and mopes; if he has irregular attacks of febrile disturbance, loses flesh, has short, dry cough, and complains of vague pains and oppression about the chest, we should suspect phthisis. If these symptoms have succeeded to an attack of measles or whooping-cough, our suspicions are strengthened; but so long as percussion of the chest shows no dulness, and auscultation reveals nothing but harshness of respiration, with here and there dry rhonchi, there is nothing upon which to found a positive diagnosis. If the dry sounds become replaced by submucous rhonchus, there is still nothing which may not be accounted for by ordinary catarrh attacking a weakly child. If, however, the dry rhonchi persist and become general, being heard from apex to base, and if this condition continues without improvement for several weeks, and without moist sounds replacing the dry râles, the case assumes a very much graver aspect, and the diagnosis of phthisis becomes almost a certainty. Such cases are, however, more common in the acute form of the disease. In chronic phthisis the tubercles have a greater tendency to become grouped at the apices, both lungs being affected. Here there is dulness on percussion, and the stethoscope reveals weak or bronchial breathing, with often increased resonance of the voice or cry. The dulness, however, to be trustworthy, must be well marked: slight shades of variation from a healthy resonance being worthless as evidence of consolidation. Should the percussion dulness be distinct, and the breathing bronchial,

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with a slight crackle at the end of inspiration, these signs occurring at both apices, and continuing unchanged for two or three weeks, become satisfactory evidence of tubercular consolidation. On the other hand, absence of dulness is no sufficient proof of the absence of aggregated tubercle, for the resonance may be due to emphysema.

In cases where, from the ill-defined character of the physical signs, we had been obliged to reserve an opinion as to the condition of the apices, the occurrence of double pneumonia at those spots throws considerable light upon the difficulty, for inflammation coming on under such circumstances greatly increases the probabilities of tubercle.

The thermometer is of little value in the diagnosis of pulmonary tubercle: a continued elevation of temperature shows the presence of tuberculosis, but this elevation is, according to Dr. Ringer's* investigations, due rather to the general condition of the body than to the actual formation of tubercle in the organs, and affords, therefore, no distinct indication of the presence of tubercle in the lungs. It may strengthen our suspicions, but that is all.

In scrofulous pneumonia we can generally succeed in discovering a distinct period at which the first symptoms were noticed. A child, delicate, but in his usual health, is seized with an attack of vomiting, followed by fever, cough, and general chest symptoms. The strength is not much reduced, and the breathing is but little oppressed, although it may be rather more hurried than natural.

If the child is seen early, no dulness may be found on percussion, but there is more or less coarse crepitation heard at a certain part of the chest, usually at one or the other apex-seldom at both if the disease is uncomplicated. The crepitation accompanies the expiration as well as the inspiration, and varies greatly in amount from day to day,

* On the Temperature of the Body as a Means of Diagnosis in Phthisis and Tuberculosis. London, 1865.