PNEUMONIA, or inflammation of the substance of the lungs, is a disease which is divided by pathologists into three distinct stages, corresponding to different degrees or periods of inflammatory action. The first stage is that of engorgement, in which the lung or a portion of it. is gorged with blood, is of a darker color externally, and crepitates (or crackles) less under pressure than healthy lung does; the air that ought to exist in the pulmonary cells being in a great measure replaced by fluid. On cutting the engorged portion the section is seen to be redder than natural, and to yield a great quantity of reddish and frothy serum. The most engorged portions will generally float in water, although they are heavier than healthy lung. If the inflammation continues, new char acters appear. The affected portion of the lung ceases to crepitate under pressure, and sinks when placed in water, in consequence of its now containing no air. The spongy character of the lung is gone. It is now solid, and the cut surface so closely resembles_ that of liver that the term Irepatization, first suggested by Laenuec, is generally applied to this stage. On examining with the microscope a torn fragment of the hepatized lung, it will be seen to be composed of small red granulations pressing upon one another, which are doubtless the air-cells clogged up, thickened, and made red by the inflamma tion. In the third and most advanced stage the pulmonary tissue remains, as in the last stage, dense, solid, and impervioug to air; but its section, iu place of being red, is now of a reddish-yellow, or straw, or drab, or stone or is of a grayish tint, and the little granulations which were red in the second stage are now whitish or gray, from the presence of pus or matter which permeates through the pulmonary tissue, rendering it very soft and friable. To this stage, which is in reality one of diffused suppuration., Laennec applied the terms gray hepatization, or purulent infiltraiton. Besides revealing to us the above information regarding the changes which the pulmOnary textures undergo in the three stages of this disease, morbid anatomy teaches, us that inflammation does not attack all parts of the lung on both sides indiscriminately. It is much more com mon on the right side of the body than the left. Of 210 cases collected by Andral, 121 were on the right lung alone, and 58 on the left side alone; while in 25 it was double (i.e., occurred in both lungs), and in six the seat wits uncertain; so that pneumonia is more than twice as common on the right side as on the left, and only occurs on loth sides together as often as once in eight times. According to Grisolle, however, whose Traite Pratique de la Pneumonia is the standard work on this disease, the relative fte quency with which the right lung is affected is rather less than two to one (11 : 6). More over, pneumonia is considerably more common in the lower than in the upper lobes of the lung—a point of great importance in diagnosis. Of 88 cases observed by Andra], the inflammation was found to affect the lower lobe 47 times; the upper lobe, 30; and the whole lung at once, 11. Inflammation of the bronchial tubes so constantly accom
panies inflammation of the tissues of the lung, that although bronchitis often exists with out pneumonia, pneumonia never occurs without bronchitis. Moreover, a certain amount of pleurisy or inflammation of the investing membrane accompanies pneumonia in a very large majority of cases.
j The alterations which take place in the tissue of the lung give rise to important modifications of the ordinary sounds yielded by auscultation and percussion, the dis crimination of which, however, belong to the physician.
Tire following are the general symptoms, as distinguished from the physical signs, of pneumonia: The disease generally commences with inflammatory fever; and pain in the side, due to pleurisy in most cases, soon supervenes. The breathing is always more or less affected, especially when the upper lobe is inflamed. According to prof. (laird ner, the dyspneea of pure pneumonia is a mere acceleration of the respiration, without any of the heaving or strainine. respiration observed in bronchitis, or in eases where the two diseases are 'combined. Dnirium is a very frequent and always a dangerous symptom, indicating that the due arterialization of the blood is much interfered with, and that the impure circulating fluid is affecting the brain. The cough is usually dry at first, but in a few hours it is accompanied by the expectoration of sputa of so characteristic a nature as to afford almost certain evidence of the presence of the disease. On the second or third day the expectoration, which previously consisted merely of a little bronchial mucus, consists of transparent and tawny or rust-colored sputa, which unite in the vessel containing them into one gelatinous mass. The color is owing to the complete blending of the blood and mucus, and in proportion to the quantity of the former the sputa is more or less deeply tinged. So long as the expectorated matter flows readily along the side of the vessel when it is tilted, there is reason to believe, unless physical signs tell us otherwise, that the inflammation is still in the first stage; but when the sputa are so viscid that the vessel may be inverted and strongly shaken without their being detached, there is reason to fear that the pneumonia has reached the second stag •. If improvement now commences, the sputa becomes less tenacious, less rust-colored. and gradually like the expectoration of common catarrh. But if the disease advances. the rust-colored sputa, although in less quantity, may go on to the end; or there may be no expectoration, either on account of its own tenacity or of the patient's want of power to eject it, in which case the air-passages get gradually filled and death from suffocation occurs; or there may be the expectoration of a fluid of the consistence of gum-watcr, and of a brownish-red color (resembling prune-juice), which, according to Andra], affords strong evidence that the disease is in its third stage; or, lastly, pure pus may be excreted during the third stage.