250 the cells but also the finer bronchi, and which speedily coagulates, causing the lung to become firmly consolidated. In this condition the cells are entirely emptied of air, their blood-vessels are pressed upon by the exudation, and the lung substance, rendered brittle, sinks in water. The appear ance of a section of the lung in this stage has been likened to that of red granite. It is to the character of the exudation, consisting largely of coagulable fibrin, that the term croupous is due. (3) Grey Hepalization. In this stage the lung still retains its liver-like consistence, but its colour is now grey, not unlike the appearance of grey granite. This is due to the change taking place in the exudation, which undergoes resolution by a process of fatty degeneration, pus formation, liquefaction, and ultimately absorption, so that in a comparatively short period the air vesicles get rid of their morbid contents and resume their normal function. This is happily the termination of the majority of cases of croupous pneumonia, yet it occa sionally happens that this favourable result is not attained, and that further changes of a retrograde kind take place in the inflamed lung in the form of suppuration and abscess or of gangrene. In such instances there usually exists some serious constitutional cause which contributes to give this unfavourable direction to the course of the disease. Further, pneumonia may in some instances become chronic, the lung never entirely clearing up, and it may terminate in phthisis. Pneumonia may be confined to a portion or the whole of one lung, or it may be double, affecting both lungs, which is a serious and often fatal form. The bases or middle of the lungs are the parts most commonly inflamed, but the apex is sometimes the only part affected. The right lung is considerably more fre quently the seat of pneumonia than the left lung. Many points in the pathology of this form of pneumonia remain still to be cleared up. Thus there is a growing opinion that it is not a simple lung inflammation, as was formerly supposed, but that, as regards its origin, progress, and termination, it possesses many of the characters of a fever or of a constitutional affection. An interesting and important fact in this connexion is the recent discovery by Friedlander and others of a micro-organism or bacillus in the blood, lungs, and other tissues in cases of pneumonia, which, when inoculated into certain lower animals, is followed by the symptoms and appearances characteristic of that disease. While it must be confessed that such inoculation experiments carried on in rabbits, guinea pigs, or mice are scarcely sufficient by themselves to settle the question of the specific and infectious nature of pneumonia as it atl ects the human subject, yet they are of distinct value as evidence pointing in that direction. Further, there are numerous instances on record in which this disease has appeared to spread as an epidemic in localities or in families in such a way as strongly to suggest the idea of infective-ness. Cases of this kind, however, are open to the question as to whether there may not coexist some other disease, such as a fever, of which the pneumonia present is but a complication. The whole subject of the pathology of pneumonia is still under investigation, and all that can in the meantime be affirmed is that it presents many features which render its phenomena unlike those of an ordinary inflammation, while on the other hand it has strong analogies to some of the specific fevers. As regards known causes, in the vast majority of instances an attack of pneumonia comes on as the result of exposure to cold as the exciting agent, while such conditions as fatigue and physical or mental depression are often traceable as powerful predisposing influences. The symptoms of acute pneumonia are generally well marked from the beginning. The attack is usually ushered in by a rigor (or in children a convulsion), together wit. i vomiting and the -speedy development of the febrile condition, the temperature rising to a considerable degree 101 to 104 or more. The pulse is quickened, and there is a marked disturbance in the respiration, which is rapid, shallow, and difficult, the rate being usually accelerated to some two or three times its normal amount. The lips are livid, and the face has a dusky Hush. Pain in the side is felt, especially should any amount of pleurisy be present, as is often the case. Cough is an early symptom. It is at first frequent and hacking, and is accompanied with a little tough colourless expectoration, which soon, however, becomes more copious and of a rusty brown colour, either tenacious or frothy and liquid. Microscopically this con sists mainly of epithelium, casts of the air cells, and fine bronchi, together with granular matter and blood and pus corpuscles. The following are the chief physical signs in the various stages of the disease. In the stage of congestion fine crackling or crepi tation is heard over the affected area ; sometimes there is very little change from the natural breathing. In the stage of red hepati/ation the affected side of the chest is seen to expand less freely than the opposite side ; there is dulness on percussion, and increase of the vocal fremitus ; while on auscultation the breath sounds are tubular or bronchial in character, with, it may be, some amount of fine crepitation in certain parts. In the stage of grey hepatization the percussion note is still dull and the breathing tubular, but crepitations of coarser quality than before are also audible. These various physical signs disappear more or less rapidly during convalescence. With the progress of the inflammation the febrile symptoms and rapid breathing continue. The patient during the greater part of the disease lies on the back or on the affected side. The pulse, which at first was full, becomes small and soft owing to the interruption to the pulmonary circulation. Occasionally slight jaundice is present, due probably to a similar cause. The urine is scanty, sometimes albuminous, and its chlorides are diminished. In favourable cases, however severe, there generally occurs after six or eight days a distinct crisis, marked by a rapid fall of the temperature accompanied with perspiration and with a copious discharge of lithates in the urine. Although no material change is as yet noticed in the physical signs, the patient breathes more easily, sleep returns, and conval escence advances rapidly in the majority of instances. In unfavour able cases death may take place either from the extent of the inflammatory action, especially if the pneumonia is double, from excessive fever, from failure of the heart s action or general strength at about the period of the crisis, or again from the disease assuming from the first a low adynamia form with delirium and with scanty expectoration of greenish or "prune juice" appearance. Such cases are seen in persons worn out in strength, in the aged, and especially in the intemperate. Death may also take place later from abscess or gangrene of the lung ; or again recovery may be imperfect and the disease pass into a chronic pneumonia. The treatment of acute pneumonia, which at one time was con ducted on the antiphlogistic or lowering principle, has of late years undergone a marked change ; and it is now generally held that in ordinary cases very little active interference is called for, the disease tending to run its course very much as a specific fever. The employment of blood-letting once so general is now only in rare instances resorted to ; but, just as in pleurisy, pain and difficulty of breathing may sometimes be relieved by the applica tion of a few leeches to the affected side. In severe cases the cautious employment of aconite or antimony at the outset appears useful in diminishing the force of the inflammatory action. AVarm applications iu the form of poultices to the chest give com fort in many cases. Cough is relieved by expectorants, of which those containing carbonate of ammonia are specially useful. Any tendency to excessive fever may often be held in check by quinine. The patient should be fed with milk, soups, and other light forms of nourishment. In the later period of the disease stimulants may be called for, but most reliance is to be placed on nutritious aliment. After the acute symptoms disappear counter-irritation by iodine or a blister will often prove of service in promoting the absorption of the inflammatory products. After recovery is complete the health should for some time be watched with care. When pneumonia is complicated with any other ailment or itself complicates some pre-existing malady, it must be dealt with on principles applicable to these conditions as they may aifect the individual case. Catarrhal or Lolular Pneumonia (Broncho-Pneumonia) differs from the last in several important pathological and clinical points. Here the inflammation is more diffuse and tends to affect lobules of lung tissue here and there, rather than one or more lobes as in croupous pneumonia. At first the affected patches are dense, non-crepitant, with a bluish red appearance tending to become grey or yellow. Under the microscope the air vesicles and finer bronchi are crowded with cells, the result of the inflammatory process, but there is no fibrinous exudation such as is present in croupous pneumona. In favourable cases resolution takes place by fatty degeneration, liquefaction, and absorp tion of the cells, but on the other hand they may undergo caseous degenerative changes, abscesses may form, or a condition of chronic interstitial pneumonia be developed in both of which cases the condition passes into one of phthisis. Evidence of previous bronchitis is usually present in the lungs affected with catarrhal pneumonia.
In the great majority of instances catarrhal pneumonia