PLEURISY is a very common disease in young subjects, and one which, al though seldom immediately fatal, often produces remote consequences of a very serious kind. In childhood the effused fluid becomes purulent at a very early period ; and the retention in the chest-cavity of a collection of purulent matter seriously hinders the nutrition of the patient, and may lead to various forms of disease, both general and local.
Causation.—Pleurisy is comparatively rare during the first twelve months of life. It becomes much more common during the second year, and after that age is one of the most frequently met with of all diseases of childhood. The inflammation may be primary or secondary. In the first case it appears to be often the consequence of exposure to changes of tem perature ; at least it is difficult to discover any other cause for it than a chill. It may be also excited by mechanical causes, such as direct irrita tion from injury to the chest-wall, or rupture into the chest-cavity of ab scesses or hydatid cysts. Secondary pleurisy may arise from extension of inflammation from the lung, the pericardium, or the peritoneum. It may occur in the course of acute rheumatism, scarlatina, measles, •typhoid fever, small-pox, and inherited syphilis ; and is very often a consequence of renal disease, and sometimes of tuberculosis.
Morbid Anatomy.—Inflammation of the pleura is usually confined to one side of the chest, and may be general over that side or limited to cer tain regions (localised or loculated pleurisy). The inflammation begins with of vessels and infiltration of the serous and subserous tissues. An effusion of inflammatory lymph then takes place, and of fluid which may accumulate to a large amount in the pleural cavity. The serous membrane is rough and lustreless, and becomes coated with a layer of effused lymph. This is at first merely a thin, coherent membrane ; but gradually its thickness increases. The surface is sometimes ribbed or honeycombed in appearance, and we occasionally see strings or bands of lymph passing be tween the opposed surfaces of the pleura, connecting them with one an other. The lymph consists of albumen, fibrine, and corpuscles derived
from proliferating epithelium. It is at first loosely attached to the serous membrane beneath, but gradually becomes more firmly adherent. Event ually new vessels form in it, so that it is organised and converted into con nective tissue. In this way the opposed surfaces become firmly united, and the pleural cavity, where these adhesions occur, is obliterated.
The effused fluid is at first yellowish or greenish, and transparent, but it soon becomes turbid and opaque, and in children very quickly puru lent. The serous effusion contains both albumen and fibrine, and coagu lates spontaneously after removal. The pus is usually quite healthy in appearance and without unpleasant smell ; but in exceptional cases it is dark coloured and very offensive. Sometimes it is stained or streaked with blood. The quantity of effused fluid is very variable. It may be merely an ounce or two, or may reach two or three pints. When thus copious, the whole side is dilated, the intercostal spaces are widened, and neighbouring organs are displaced. The lung is compressed, and if, as sometimes happens, although very rarely in the child, it is bound clown by a thick layer of false membrane, it may not expand again as the fluid be comes absorbed. In that case it leads to the same deformities as are no ticed under similar conditions in the adult. It is, however, very rare to find a greatly contracted chest from an old pleurisy in the child. Even if the chest fall in at first, it will be often found to right itself in a surprising way in the com-se of time ; and a child who was left with curved spine and retracted ribs may be seen again, after an interval of twelve months, with a chest as symmetrical as if it had never been affected. It is rare to find a child permanently deformed by this means.