Part 36

Post Mortem Appearances. These consist mainly in the presence of false membranes lining the pleura and hanging in cobweblike shreds into the cavity of the chest, and of the liquid effusion which fills up the chest at its most dependent part. The pericardium also contains fluid in many cases. The periods at which exudation takes place, and when the principal changes take place in the exuded materials have been well investigated by Dupuy, Hamont, Delafond and St. Cyr. They induced pleurisy by injecting irritant liquids into the chest, and noted the regular sequence of changes.

Dupuy injected two drachms of oxalic acid dissolved in three ounces of water. Symptoms of pleurisy at once came on, with the friction sound characteristic of its early stages. Next day friction sound had ceased and evidence of effusion existed. The same experiment repeated on several horses showed that if killed at any period subsequently to this, considerable exudation had already taken place. In one horse in which the disease was of 50 hours’ standing the chest contained 43 pints of citrine-colored fluid, and abundance of yellow, thick, false membrane enveloping the costal and pulmonary pleuræ.

Hamont injected seven ounces of a weak solution of tartaric acid into the left pleural sac, repeated the injection next morning and destroyed the horse twenty minutes afterward. The chest opened immediately showed a small amount of liquid on the affected side, and the pleura injected and reddened.

Delafond made twenty-two experiments with the same general result.

Percivall found recent adhesions between the lungs and side so early as seventeen hours after the commencement of the pleurisy.

Andral injected rabbits with acetic acid and in nineteen hours found in the injected pleura soft, thin, false membranes traversed by red anastomosing lines, and in certain cases a serous or puriform fluid.

W. Williams found a false membrane formed twenty-four hours after the injection of the irritant.

St. Cyr in a series of 43 experimental and casual pleurisies in horses, found that in a very few hours there was marked local congestion and swelling of the pleura speedily followed by the formation of soft, pulpy, friable false membranes, largely amorphous and granular but impregnated with many cells and nuclei. These adhere feebly to the pleura but may accumulate with prodigious rapidity so as to cover in three or four days the whole pleural surface on one or both sides. The attendant serous effusion was bloody, turbid, or lactescent. The pleural surface under the false membrane was highly vascular and studded with fragile, red conical elevations projecting into the membrane. Exceptionally the sub-serous connective tissue became the seat of exudation as well.

From the sixth to the ninth day the false membranes began to become vascular and from the tenth to the fourteenth day commenced to organize into the connective tissue. With the advent of this stage, the inflammatory action tended to subside, and the reabsorption and repair to ensue.

Pleuritic effusion. This varies greatly at the different stages of the disease. As effused it has a composition resembling that of the blood:—

Water, 911 to 924 Albumen, 63.33 to 82.50 Fibrine formers, 2.16 to 12.50 Extractive matter. Salts.

The progressive changes from the hæmorrhagic effusion to the limpid hydrothorax and their relation to the different stages of the disease and the subsidence of the inflammation are of the greatest importance in deciding questions of responsibility, when the animal has recently changed hands. St. Cyr has classified his cases in the following instructive table:

─────────────────────┬─────────────────────────────────────────┬─────── Duration of the │ │ Disease. │ Effusions. │Total. ─────────────────────┼──────┬─────────────────┬────────┬───────┼─────── │ Port │ │Muddy or│ │ │Wine. │Sero-sanguineous.│Grayish.│Limpid.│ ─────────────────────┼──────┼─────────────────┼────────┼───────┼─────── From 1st to 7th day.│ 9│ 6│ 3│ │ 18 „ 8th to 15th day. │ 2│ 3│ 4│ 6│ 15 „ 16th to 30th day. │ │ 1│ 1│ 5│ 7 After 30th day. │ │ │ │ 3│ 3 ─────────────────────┼──────┼─────────────────┼────────┼───────┼─────── │ 11│ 10│ 8│ 14│ 43 ─────────────────────┴──────┴─────────────────┴────────┴───────┴───────

Up to the 7th day 50 per cent. were dark red; after the 7th day only 13.3 per cent.; and after the 15th day none. Up to the 7th day 83.3 per cent. were either dark red or sero-sanguineous and not one had attained to translucency. After the 7th day only 8 per cent. were of port wine hue, and by the 15th day 24 per cent. of all cases of over seven days standing were already transparent. Of all cases of over 15 days standing, 80 per cent. were perfectly translucent and none showed the dark red hue. Finally after the 30th day all remaining cases were limpid. This of course must not be applied with the same confidence in both directions. While translucency of the effusion bespeaks seven days standing and probably fifteen or twenty, the dark red hue must not be held to imply a recent date for the attack. A relapse in the course of convalescence may easily and quickly stain anew a liquid that was already limpid, or had advanced far toward this condition.

The appearance of the lung tissue in a case of confirmed pleurisy is characteristic. The lung is of a dull red color, shrunken, slightly collapsed, flabby, scarcely crepitant under pressure and heavier than water or floating in water. It is tough, not friable like hepatized lung, and its cut surface is dry, smooth, and presents the interlobular septa very well marked. This is due to the compression by effused liquid, and by the organizing and contracting false membranes covering the lung and implies nothing more than simple condensation. The air cell may be collapsed, but contains no new product and has not parted with its epithelium and the lung can be inflated through the bronchia.

Differentiation according to the nature of the effusion. Pathologists have divided acute pleurisy into the dry, sero-fibrinous, and sero-fibro-purulent.

=1. Dry or fibrinous pleurisy= has usually a more acute type and the exudate containing an excess of the fibrinogenous elements forms a coagulum or false membrane on the affected surface tending to bind that to the part adjacent—the lungs to the costal pleura. The serum, small in quantity, is in the main retained in the exudate or if set free is actively reabsorbed by the healthy pleura.

=2. Sero-fibrinous pleurisy.= This form is usually less acute and more extended involving perhaps an entire pleural sac, or even both sides of the chest. This is the common form of pleurisy and is that referred to in the experiments of St. Cyr and others above. The earliest lesions in experimental cases (with chloride of zinc solution) in dogs are an uniform bright red congestion, with a bright, shining surface as yet perfectly dry. There is already shedding of patches of the endothelial cells, swelling and proliferation of the superficial connective tissue cells and the formation of a few pus globules. This is seen in from half an hour to six hours after the application of the irritant.

Next follows the exudation of fibrine and serum, which respectively coagulate as false membrane on the inflamed membrane, or drop to the bottom of the sac as liquid. The fibrine appears as granules, little knobs and threads between and on the endothelial cells and entangling a few pus cells. The changes are now much more marked in the connective tissue cells, which are more numerous, larger, nucleated and often stellate or polygonal. Changes are well advanced in twenty-four hours. The cells go on increasing to the fourth or fifth day, when new blood vessels are formed into the membrane and may be injected from the pleura. From this time, in favorable cases absorption of the liquid proceeds, and the fibrine is organized, and by the fourteenth day is transformed into connective tissue, the superficial cells forming endothelium and the deeper, branching connective tissue cells. The result is the thickening of the pleura and the formation of adhesions. The case, however, may prove fatal, or it may be protracted through the continued production of fibrine and serum, or it may pass into empyema.

=3. Sero-fibrino-purulent pleurisy.= =Empyema.= This is usually very dangerous as well as complicated. It may supervene on the last described form. It may depend on rupture into the pleura of abscess of the lung, bronchial glands, liver, diaphragm or intercostal space and the infection of the chest cavity. It may in the same way follow the laceration of a bronchium by a broken rib, the perforation of the intercostal space by a foreign body, or (in cattle) the penetration of the chest by a sharp pointed body from the reticulum. It may follow at once on pleurisy of a very high grade. Probably in all such cases there is infection of the pleura by pus microbes. When there is a communication with a bronchium, the reticulum or the external air there are usually septic germs in addition, and the contents of the chest become fœtid.

The purulent fluid may accumulate in the lower part of the pleural sac, or it may be confined in abscess form in the false membrane, and extend thence into surrounding tissues. The pus-containing pleura, or cavity infected by the pus germs, assumes the appearance of a granulating surface, or of the lining membrane of an abscess, and continues to produce pus in greater or less amount.

The formation of pus in the pleura is known as empyema. When air enters the pleura through a wound perforating the chest wall, or when gas is formed in the pleura, the condition is =pneumothorax=. As liquid is usually present as well it is =hydro-pneumothorax=.

Tubercular and other forms of pleurisy have in certain cases been superadded to the specific local lesions, by which such diseases are individually characterized.

Prognosis. Occurring in an otherwise healthy system and especially if confined to one side of the chest, pleurisy is not frequently fatal, and under appropriate treatment recovery is oftentimes rapid and satisfactory. A certain number of cases merge into chronic hydrothorax, the inflammation apparently subsiding, but reabsorption failing to take place. The hydrothorax may last for months or even a year.

Treatment. If seen during the chill and before inflammation has been definitely established every effort must be directed to secure its abortion, if possible. No time should be lost in placing the patient in a warm comfortable stall or box, covering him with woolen blankets and actively rubbing and loosely flannel bandaging the legs. Warm drinks and warm injections must be given. Half an ounce or an ounce of camomile or boneset in infusion in two or three quarts of hot water, or in the absence of this any of the carminatives, or etherial, alcoholic or ammoniacal stimulants may be given. Pilocarpin in 7 grain dose hypodermically may promptly secure a revulsion of blood to the skin and at once overcome the chill and prove a most effective derivative from the pleura. Placing the legs in buckets of hot water, or the whole animal in a hot air bath will often act equally well. Packing the chest and even the abdomen in a blanket wrung out of very hot water and covering it closely by one or two dry ones, or, better still, by a rubber or other impermeable covering, will long retain both heat and moisture, securing free cutaneous circulation, and soothing in a most effective way the irritation in the chest. This may be maintained as long as requisite to relieve the patient, and then the body may be uncovered, a part at a time, rubbed dry and covered with a dry woolen blanket. By using elastic circingles over the compress they are adapted to the respiratory movements and any restriction in the movement of the ribs is beneficial by limiting the friction, pain and irritation in the pleura.

In the second stage, when inflammation has already set in, the same general measures of derivation toward the skin and hot bath or soothing derivative compress are still demanded though they may be substituted by more stimulating derivatives. The bleeding of the patient into his own vessels is sought in various ways. On the continent of Europe stimulating embrocations (essential oils, ammonia and oil, mustard, etc.) are applied to the limbs. In America and England similar agents are more commonly applied to the walls of the chest and dry cupping in the same region has been resorted to. Metallic cups with small mouths and having a capacity of about a pint each, have the air rarefied by plunging into each a spirit lamp, and, on its withdrawal, suddenly applying the mouth of the cup on the skin of the costal region previously well coated with lard. Another form of cup is made with a tube and stopcock in its otherwise blind end by means of which it is exhausted with a syringe after its mouth has been applied to the skin. In the absence of both a narrow mouthed glass tumbler may be employed, the air is rarefied by inserting into it a burning spill of paper or wood for a few seconds and on its withdrawal the cup is instantly inverted on the skin. If the animal is very hairy or very thin it may be necessary to shave the part, and smear with oil and even to select a very narrow mouthed cup. When applied the cup is cooled with water or otherwise and owing to the partial vacuum the skin is strongly drawn up into it and the blood accumulates in and under the skin. It may be kept on for half an hour at a time and with ten or twelve cups on one side the patient tends to profuse perspiration establishing a strong revulsion toward the skin, and great relief. In dangerous cases three or four applications may be required in twenty-four hours.

Next to this the mustard application is perhaps the safest and most valuable. The best ground mustard (black by preference) is made into a very thin pulp with tepid or cold (never hot nor boiling) water and rubbed in against the hair so as to soak the surface of the skin; it is then closely covered with paper and with a rubber or other impervious covering or, in default of better, with a close blanket and left on for two hours. By this time the skin should be thickened to the extent of at least a quarter of an inch and the derivation and relief will be very manifest.

Cantharides is sometimes used but like most other severe irritants, is liable to induce sympathetic irritation in an already severely inflamed pleura, and thus to obviate all benefit. Cantharides is also liable through extensive absorption to irritate the kidneys. To counteract this Bouley gave ½ drachm doses of camphor with alleged good effect.