proceeds from the conditions relating to the blood and circulation, on which dropsical effusion in other situations depends. It rarely occurs alone, but is generally an element of general dropsy; that is, dropsical effusion exists. at the same time in the peritoneal cavity and in the subcutaneous areolar tissue, constituting either oedema or anasarca.

The signs which denote the presence of liquid in the pleural cavity are alike applicable to inflammatory and dropsical effusion. The proof afforded by the change of level of the liquid, corresponding with changes of the position of the body, is more constantly available in hydrothorax, because lymph is not present to agglutinate the pleural surfaces and lead to permanent adhesions. But the distinctive feature of this affection is the existence of effusion in both pleural cavities. Hydrothorax is always double, provided the pleural cavity on one side be not abolished by universal adhesions due to a previous attack of pleuritis. Primary pleuritis, on the other hand, is almost always single. The amount of dropsical effusion, however, in both sides is not always uniform. It is not uncommon to find in the pleural cavity on one side a quantity of liquid considerably larger than is contained in the cavity on the other side. It may then be laid down as a rule, that if the physical signs show the presence of liquid in both sides, and general dropsy coexist, the affection is hydrothorax. A friction murmur is, of course, not developed in this affection.

Symptoms denoting inflammation, viz., pain, cough, febrile movement, do not belong to the clinical history of hydrothorax. The respirations are increased in frequency, and the patient suffers from deficiency of breath, or dyspnoea, in proportion to amount of dropsical effusion. Existing in both sides, it is obvious that the embarrassment of respiration will be the same as if all the liquid were in one pleural cavity, and twice as much as if the effusion in one side were unaccompanied by an equal effusion in the other side. If there be considerable effusion, dyspnoea will be marked, amounting perhaps to orthopnoea, and death by apnoea may be due to the amount of effuCardiac lesions, producing obstruction of the mitral orifice, especially favor the occurrence of hydrothorax, after these lesions have led to dilatation of the right cavities of the heart.

The measures of treatment in hydrothorax are those indicated in general dropsy, and need not be considered in this connection. It is certainly very rarely the case that the affection occurs under circumstances calling for paracentesis; but this operation is admissible, as a palliative measure, if the amount of effusion be sufficiently large to occasion great suffering or endan ger life.

CHAPTER IV.

PNEUMONITIS.

Seat of the Inflammation-Varieties-Acute Lobar Pneumonitis-Anatomical CharactersLaws of the Disease-Clinical History-Pathological Character-Causation-DiagnosisPrognosis.

HAVING considered in the preceding chapters inflammation affecting the serous membrane investing the lungs, inflammation seated in the pulmonary substance or parenchyma is next to be considered. The latter is called pneumonitis or pneumonia. The question at once arises, what constitutes

the parenchyma, or substance of the lungs. These terms relate to the aircells or vesicles, together with the bronchioles or terminal bronchial branches. These are lined by a membrane differing materially from the mucous membrane lining the successive divisions of the bronchial tubes. The membrane which lines the air-cells and bronchioles is distinguished by its tenuity, by the absence of mucous follicles, and by a change of epithelium from the cylindrical and ciliated to the squamous or tessellated. The air-cells and bronchioles make up the lobules, and these, united by means of areolar tissue, constitute the lobes into which the two lungs are divided. The inflammation in pneumonitis is seated in the membrane lining the air-cells and bronchioles. The differences in the structure of this membrane, as compared with the bronchial mucous membrane, together with a difference of function, will serve to explain the fact that the inflammation in pneumonitis may be limited to the pulmonary substance, and also, that in bronchitis the inflammation does not extend to the pulmonary parenchyma. This is in accordance with a pathological law, viz., that inflammation seated in a structure does not, as a rule, extend to another structure, however proximate, which has important anatomical differences, or differs as regards its functions. Some striking examples of conservatism in disease will be found to hinge upon this pathological law.

Pneumonitis, when not developed as a complication of an existing pulmonary disease, usually affects, at least, an entire lobe; and this extension of inflammation is expressed by the term lobar pneumonitis. Developed in the course of another pulmonary disease, it may be more or less limited. When limited to a portion of a lobe, it may be distinguished as circumscribed pneumonitis. The inflammation, in the great majority of cases, is acute, but it occurs in a chronic form. Chronic pneumonitis will be noticed under a distinct head. Affecting children, pneumonitis has been supposed to differ from the disease in adults in affecting isolated lobules, more or less in number, in both lungs, and the term lobular pneumonitis has been used to express this distinction. The occurrence of lobular pneumonitis will be considered under the head of pneumonitis in children. Acute lobar pneumonitis will be first considered.

ACUTE LOBAR PNEUMONITIS.

ANATOMICAL CHARACTERS.-The first appreciable change resulting from acute inflammation is the same here as in other situations, viz., an abnormal accumulation of blood, or hyperæmia, due to active congestion or engorgement. The inflamed portion of the lung is heavier than in its healthy state; on section, the cut surfaces present a dark appearance, and blood flows in abundance, together with serous liquid more or less frothy. It would not be easy to discriminate between hyperemia arising from inflammation and that due to hypostatic congestion, by the appearances. But the latter affects the portions which are dependent and is not limited to one lung, while the former is confined to one side and not always limited to the position into which the blood would accumulate by gravitation. So long as no change beyond hyperæmia has occurred, the air-cells contain air, and, after removal of the blood by maceration and pressure, the pulmonary structure is found to be intact. This condition lasts but for a short period.

Exudation speedily follows. A coagulating material escapes from the blood, and coagulates within the air-cells. The cells are filled and distended with the exuded matter. They cease to contain air. The lung is solidified, presenting an appearance not unlike that of the liver, and hence this condition has been called hepatization. In this condition usually the lung contains

but little blood, and presents a pale, anæmic aspect; hence the term red hepatization is inaccurate. Closely examined, the cut surfaces have a granular appearance. More or less liquid escapes when the hepatized part is divided, containing no air bubbles. The substance of the lung is softened, breaking down under the pressure of the finger more readily than in its healthy state, that is, it is more friable. Its weight is much increased. A single lobe solidified by inflammatory exudation increases in weight from one to two pounds, and an entire lung solidified may acquire an additional weight of four pounds. This increase in weight is due, not to an accumulation of blood, which is less than in health, but to the amount of solid matter withdrawn from the blood. Owing to the absence of air, portions of the solidified lung sink when thrown into water. The volume of the affected lobe or lobes is large in proportion to the amount of exudation, and no collapse occurs when the chest is opened.

If the progress of the disease be favorable, the exudation is removed mainly or exclusively by absorption. It may be absorbed with great rapidity. After its removal, the air-cells are found to have sustained no damage. The pulmonary structure remains intact during the continuance of the deposit, and its functional capacity is fully restored after the deposit disappears. circulation, too, is again restored as in health, and the recovery of the affected part is complete.

The

If the progress of the disease be unfavorable, suppuration takes place, and the affected lobe or lobes are infiltrated with pus. This condition is called purulent infiltration. The lung presents a grayish appearance. divided, pus flows freely from the cut surfaces. The substance is much softened, breaking down on slight pressure. Occasionally, collections of pus take place forming pulmonary abscesses. Gangrene of the affected portion of lungs sometimes occurs, but this, as well as the occurrence of abscess, is extremely rare.

Pleuritis, limited to the affected lobe or lobes, usually occurs and is developed coincidently with the pneumonitis. In a small proportion of cases the concurrent pleuritis is wanting. It varies much in degree in different cases, being sometimes slight and sometimes severe. The exudation of lymph on the pleuritic surface over the affected lobe or lobes, varies in amount. Much liquid effusion into the pleural cavity occurs only as an exception to the rule; the pleuritis, in most cases, is circumscribed and dry. The terms peripneumonia and pleuropneumonia denote the coexistence of pleuritis and pneumonitis. Inasmuch as pleuritis is very rarely wanting, these terms are applicable to nearly all cases of pneumonitis. They are sometimes applied to distinguish cases in which the pleuritis is unusually prominent and attended. with more or less liquid effusion. It is quite unnecessary to consider these terms as denoting a distinct variety of pneumonitis.

More or less bronchitis affecting the bronchial tubes within the affected lobe or lobes usually exists with pneumonitis. In some cases, however, the pneumonitis passes through its own course without affording any evidence of this limited bronchitis. Bronchitis affecting the bronchial tubes of both lungs is sometimes, but rarely, present with pneumonitis. When these two affections are combined it is accidental; bronchitis, as the primary affection, does not tend to the development of pneumonitis, and the latter has no tendency to give rise to the former.

To the foregoing sketch of the anatomical characters may be added certain laws of the disease, which are best presented in this connection. One of these relates to the situation of the disease. Pneumonitis attacks, in the great majority of cases, the lower lobe, and the lower lobe of the right, oftener than of the left, lung. Exceptionally it sometimes attacks primarily an upper

lobe, and in these cases, as a rule, the disease is more severe; but to this rule there are exceptions. The disease very rarely, if ever, attacks two lobes simultaneously, but it invades, not unfrequently, a second and even a third lobe. The inflammation does not extend from one lobe to another, but whenever a new lobe is affected, it is the seat of a new invasion. The lobes of one lung may be successively invaded, or a single lobe on both sides, or an entire lung being first affected, a lobe of the other lung may be attacked. In the two latter cases the pneumonitis is said to be double.

The inflammation extends at least over an entire lobe, as the name lobar pneumonitis implies, in the great majority of cases. There are some exceptions to this rule. I have known some instances in which the physical signs clearly showed the occurrence of inflammation extending over a limited area, without any evidence of the circumscribed pneumonitis being a complication of any other pulmonary disease. In a lobe invaded secondarily, that is, one lobe being already affected, the inflammation is sometimes found after death to have extended over a portion only of the lobe. This fact I have repeatedly noted, but perhaps if the life of the patients had been prolonged, the whole of the lobe would have been affected.

The whole of a lobe first invaded is not at once affected. The inflammation begins at a certain point, and extends from lobules to lobules until the entire lobe is involved. The point of departure may be at either the upper or lower extremity of the lobe, and at either the superficies or the centre of the lobe. The diffusion of the inflammation over the lobe takes place with more or less rapidity. Sometimes a few hours suffice, but in some cases it occupies several days. The progress of the solidification from the exudation may be determined very accurately from day to day, or from hour to hour, by means of physical signs.

The inflammation very rarely ends with the occurrence of engorgement only, without exudation. Solidification almost always occurs, and, when the inflammation is not secondary to another pulmonary disease, usually extends over the lobe or lobes invaded.

With respect to the situation and extent of the affection, the following are the results of an analysis of 121 cases: In 29 cases it was limited to the lower lobe of the right, and in 25 cases to the lower lobe of the left lung. It extended over the whole of the right lung in 27, and over the whole of the left lung in 9 cases. It was limited to the upper lobe of the right lung in 8, and to the upper lobe of the left lung in 3 cases. It was seated in the lower lobes of both lungs in 8 cases. The cases analyzed were recorded during a period of twelve years, 57 of the cases having been observed at Buffalo, N. Y., 53 cases at the New Orleans Charity Hospital, and 11 cases at the Louisville Marine Hospital.

CLINICAL HISTORY.-The division of the career of acute pneumonitis into stages, is based upon differences as regards the anatomical characters at different periods of the disease. The first stage embraces the period during which the affected lobe is in the state of active congestion or engorgement. This stage is called the stage of engorgement. The disease is considered as passing into the second stage, when the affected lobe, or a greater part of it, has become solidified by the inflammatory exudation. This stage is called the stage of solidification or hepatization. In the third stage the affected lobe is in one of two conditions. If the disease pursue a favorable course, the third stage begins when it is evident that absorption of the exuded

Clinical Report on Pneumonia, based on an Analysis of 133 Cases. By the Author. Vide American Journal of the Medical Sciences, January, 1861.

matter is going on, and convalescence takes place during this stage. This may be called the stage of resolution. If the disease pursue an unfavorable course, the third stage is one of suppuration or purulent infiltration, and this stage may be called the purulent or suppurative stage. If this stage occur, the disease generally ends fatally.

The duration of each of these stages varies much in different cases. The stage of engorgement may last but for a few hours. I have known an entire lobe to be solidified by two pounds of exudation matter, as determined after death, in less than twelve hours. Not unfrequently this stage does not extend beyond twenty-four hours. But sometimes the solidification occupies two, three, or four days. In some cases it occupies even a longer period. In the majority of cases this stage is from twenty-four to forty-eight hours in duration. The stage of solidification may also be of short duration. I have known resolution to commence and make considerable progress in twenty hours. But its commencement may not be evident for two, three, or four days, or even for a considerably longer period. In the majority of cases the duration of this stage is from two to four days. The stage of resolution is still more variable. There is a notable difference in different cases as regards the rapidity or slowness with which the solidifying deposit is removed. It is very rarely the case that the resolution is completed in less than three or four days, and generally eight or ten days are required. In some cases two or three weeks elapse before the air cells are restored to their normal condition, and occasionally the resolving process is even more protracted. If the disease pass into the purulent stage, death usually takes place within a few days; but if the disease end in recovery, many days and perhaps weeks elapse before the normal condition is restored.

In the great majority of cases, acute pneumonitis commences with a well pronounced chill, frequently accompanied by rigors. The invasion is usually abrupt, with few or no premonitions. The attack is apt to occur during the night. Coincident with or speedily following the chill, is the occurrence of pain. The pain is frequently severe. It is acute, lancinating, and, in all respects, identical with the pain in acute pleuritis. It proceeds, certainly in most cases, from the pleuritis developed in conjunction with the pneumonitis. As a rule, the intensity of the pain is in proportion to the amount of coexisting pleuritis; but it is true alike of pleuritis thus developed as a complication and when it occurs primarily, that it is sometimes attended with little or no pain. Cases of pneumonitis differ considerably as regards this symptom. It may be quite prominent, or present in a moderate degree, or altogether wanting. The pain is usually referred to a circumscribed space at or near the nipple of the affected side. This limitation of the pain is a point distinctive of pneumonitis as compared with pleuritis.

Cough is usually present at, or soon after, the invasion. It is more or less prominent. It is sometimes wanting. It is painful in proportion as pain is a prominent symptom irrespective of the cough. The cough is frequently accompanied by expectoration. The matter at first expectorated is scanty, transparent, and viscid; and in a certain proportion of cases it soon assumes characters which are highly distinctive of the disease. It becomes semi-transparent, adhesive, and has a reddish tint, like that of iron rust; hence, it is commonly known as the rusty expectoration. This appearance is due to a small quantity of blood which has become intimately mixed with the matter in its passage from the smaller to the larger bronchial tubes. The adhesiveness is such that when a considerable quantity has accumulated, it adheres so closely to the bottom of the vessel as to remain when the vessel is inverted. The rusty expectoration is by no means uniformly present. Sometimes it is semi-transparent and adhesive without the reddish tint. It