Part 32

=Direct irritation= by inhalation of smoke and other products of combustion; or acrid or irritant gases or dust; by the drawing of food by aspiration into the lungs (as in paralysis of the larnyx or pharnyx, choking, apoplexy, vomiting, etc.); by pouring irritant or insoluble drugs (oil, lard) through the nose; by the pressure of neoplasms (actinomycosis, tubercle, glanders, cancer); or by the presence of parasites (strongylus, distomata, echinococci, linguatulas).

Pneumonia from =Contusion= of the chest, fracture of a rib, or puncture or laceration of the lung is recognized.

=Contagion.= The presence of a contagium in pneumonia is today well established. Clinical observation had indicated this even before the discovery of a specific germ, but recent bacteriological investigations and the transmission of the disease by inoculation of artificial cultures have definitely settled the question. It does not follow that all cases are contagious, nor equally so, but the recognition of the contagious form satisfactorily explains the prevalence of the disease in one stable while an adjoining one escapes, and the eruption of new cases in a stable after an animal affected with the disease or convalescent from it has been introduced. It has been objected that many horses stand in the stable with pneumonia cases and escape, but so is it with glanders, cowpox, and many other affections. It merely argues an immunity in the case of some, and for the disease germ a very limited transmissibility through the air. The further objection that the existence of lesions in the lung before the onset of fever, excludes this from the list of infectious diseases, is untenable since many undeniably contagious diseases, like cutaneous anthrax, glanders, lung plague, cowpox, appear locally before any constitutional disturbance occurs, which later as the result of extensive local disease and the circulation of toxins in the blood. It places contagious pneumonia however in that long list of infectious diseases which develop first locally in the seat of infection and later become more or less generalized.

It must be admitted however that the germ of pneumonia is not the same for all cases of the disease and for all genera of animals. It must also be allowed that the same germ does not always maintain the same degree of virulence, and that it may even live for a time on the buccal mucosa of an animal belonging to a susceptible genus without any morbid result. In short we must recognize that different germs of pneumonia may become temporarily non-virulent or only slightly virulent, and remain pathologically quiescent, as for example during the summer months, to reassert itself later when the conditions become more favorable to its pathogenesis.

BACTERIOLOGY.

a. BACILLUS OF FRIEDLÄNDER. This is a short rod with rounded ends, often merely oval, occurring in pairs, or chains of four, and under given circumstances surrounded by a transparent gelatinous capsule. It is ærobic, nonmotile, does not liquefy gelatine, nor sporulate, and in gelatine stick cultures has a nail-like growth. This was found by Friedländer, Frobenius, Weichselbaum and Wolf in the pulmonary alveoli in a small proportion of cases of croupous pneumonia in man. The cultures, injected into the lungs of animals, killed one dog (out of five), six Guinea pigs (out of eleven), and thirty-two mice (all the injected). Lesions were intense congestion of the lungs, seropurulent pleural effusion, and enlarged spleen, while the bacillus swarmed in the blood and exudate.

MICROCOCCUS PNEUMONIÆ CROUPOSÆ. First found by Sternberg in his own saliva in health, and by Pasteur in the saliva of a rabid child. Afterward found in the great majority of lungs affected with croupous pneumonia in man, by Talamon, Salvioli, Sternberg, Fränkel, Weichselbaum, Netter, Gamalei, etc. Later it was found in meningitis, in ulcerative endocarditis, in arthritis, in otitis media, and in acute abscess in man.

It is a spherical or oval coccus, arranged in pairs, in fours, or exceptionally in eights or tens. Lanceolate forms are the rule in the blood of animals, and circular in artificial cultures. It stains readily in aniline colors and by Gram’s method, grows in ordinary culture media, at 37° C. in the absence of free acid, and in gelatine stick cultures as small, white colonies along the line of culture, without liquefying the gelatine. It dies in ten minutes at 52° C. (Sternberg). Its virulence lessens in artificial cultures, but is restored by passing through the body of a susceptible animal.

Injection into the lungs or trachea of rabbits, mice, sheep and, less certainly, Guinea pigs, produced distinct fibrinous pneumonia filled with the microbe. In dogs, subcutaneously, it caused abscess, but in the lungs an acute fibrinous pneumonia which only exceptionally proved fatal, recovery usually taking place in ten to fifteen days.

Klemperer induced immunity, sometimes lasting six months, by intravenous injection of filtered cultures.

DIPLOCOCCUS PNEUMONIÆ EQUINA. First found by Schütz in the lungs of pneumonic horses in 1887. It is an oval coccus arranged usually in pairs or in threes or fours, and surrounded by a transparent envelope. It stains in aniline colors but not by Gram’s method. It is ærobic and grows in gelatine at ordinary temperature without liquefying it, and in stick cultures forms a line of small, white, separate colonies which do not coalesce by growth. Does not grow on the surface of the gelatine around the puncture. Line cultures on agar are in colonies like minute transparent droplets. In bouillon it develops long chains.

Inoculated on the rabbit, Guinea pig and mouse, it produced death with pneumonic affections (hæmorrhagic congestion or inflammation), but it failed to take in some of the rabbits and Guinea pigs. Chickens and pigs proved immune. Injected into the horse’s lung or as spray into the trachea it produced true croupous pneumonia. Fiedaler and others obtained similar results. Peter has found the fæces of pneumonic horses virulent, an important point in connection with disinfection.

Schütz found that 20 grammes of the culture, in an equal quantity of boiled water, injected into the horse’s trachea, produced a rise of temperature by two or three degrees, with rigors, cough, accelerated pulse, elevated temperature, dyspnœa and prostration, but that this subsided in a few hours. By repeating this every thirty-six hours, the fourth or fifth would fail to produce a reaction and the subject proved immune.

CADEAC’S DIPLOCOCCUS PNEUMONIÆ EQUINA. In the lungs of cases of contagious pleuro-pneumonia of the horse Cadeac found a round noncapsulated coccus appearing in pairs, or rarely in chains, and staining by Gram’s method. It grew slowly in bouillon and agar at 37° C., forming on the latter in twenty-four hours, a thick, whitish, oily drop, which, as it grew larger, assumed a silvery whiteness, and dried in the centre. In bouillon it precipitated a powdery sediment. The reaction of the culture medium was unchanged. It lost virulence rapidly in artificial cultures or by a heat of 50° C., and it died in ten minutes at a temperature of 60° C. Virulence was long retained when dried, or even in putrid material.

This proved infecting to the ass, rabbit and Guinea pig, while the cat and white rat proved immune. Intratracheal injection of the dog produced a transient pneumonia. The ass inoculated with the blood of the infected rabbit died in three days, with a hepatized lung, pleurisy, and swarms of the microbes in the lungs, blood and internal organs. Rabbits injected intravenously had enlarged spleen, reddish exudate in the serous cavities, urine stained with hæmoglobin, and lungs and kidneys congested. With intratracheal injections the lesions were exclusively pulmonary. The pulmonary lesions were less constant in the Guinea pig. Weakened virus caused pulmonary lesions only without septicæmia.

It has been suggested that this coccus is at least closely related to that of pneumo-enteritis of the horse.

Symptoms. The onset of pneumonia is not often seen by the veterinarian, who is called in only after the cough, loss of appetite, hurried breathing and rigor has revealed illness to the attendants. Hence perhaps chill and rise of temperature have been placed among the earliest symptoms. The symptoms are more violent in the racer, trotter and other nervous animals. Trasbot positively claims, that considerable pulmonary inflammation and even exudation have taken place before there is any chill or rise of temperature. This is especially the case in the heavy lymphatic races of draught horses, which often according to this author perform their usual work for days after inflammatory exudation has set in. A fair counterpart of this is found in lung plague of cattle and it would indicate that both start from a local infection, which gradually extends until the systemic derangement is induced. As usually seen, and especially when it follows exposure to severe cold, a staring coat or a shivering fit usher in the disease, the degree of the chill bearing some ratio to the coldness of the air and to the future severity of the malady. This may be accompanied by a small, dry cough, but without any other marked sign of lung disease. With the access of the hot stage the characteristic symptoms of lung disease are manifested, at first resembling those of congested lungs, but less severe than those given under that head. There is a distinct increase of the body temperature; the visible mucous membranes are suffused with a blush; the expired air feels hot upon the hand; the breathing, 30 to 40 per minute, is short and accompanied by much lifting of the flanks—(labored); the cough is deep as if coming from the depth of the chest, but not so hard nor so painful as in bronchitis; the legs are placed apart, the elbows turned out and the head protruded to facilitate breathing; the nose is turned to an open door or window if any such is available; the contraction of the muscles of the face, the dilated nostrils and the retracted angle of the mouth give an anxious expression to the countenance; the eyes are semi-closed; the pulse full but soft—(oppressed)—, beats from 48 to 70 per minute; the bowels are slightly costive, the urine scanty and high colored; the skin inelastic—hidebound—harsh and dry, though sweats may bedew it in parts; the loins insensible to pinching; and if there is any discharge from the nose it consists only in a reddish—rusty—colored mucus.

=Auscultation= and =percussion= complete the diagnosis. At the outset the inflamed portion of lung, usually near its lower part, conveys a crepitating sound to the ear, but as consolidation extends the healthy murmur and the crepitating râle are alike suppressed over the whole extent of the hepatised portion around the margin of which a line of crepitation betrays the limit of the advancing inflammation. A similar line of crepitation encircles the hepatised mass even when the exuded products are being absorbed and when the lung is being cleared up and restored to its healthy state. Thus the advance of the inflammation, and the progress of recovery can be equally followed by the crepitation which, in the different circumstances, betokens active inflammation or active absorption. When both lungs are involved the posterior parts are chiefly implicated, while if the pneumonia is single it may attack the anterior, median or posterior part, or the entire lung may become consolidated. If hepatisation exists in the anterior part of the lung the thick fleshy shoulder will forbid any satisfactory examination, but if in the middle portion only, while the respiratory murmur is lost it will be replaced by a strong blowing sound (bronchial respiration) because the noise of the air rushing through the larger bronchial tubes to the posterior healthy part of the lung is conveyed with greater force to the ear through the consolidated lung tissue. This is audible from the lower third of the chest to the upper limit of hepatization. The respiratory murmur in the healthy lung is always louder than is natural.

=Percussion= confirms these results. Over the hepatised lung where no respiratory sound remains, a dull, dead sound only is brought out by the impulse of the fingers or closed fist, comparable to that obtained by percussion over the muscular masses of the shoulder or haunch, and forming a marked contrast to that obtained over the surrounding healthy lung. There is not that tenderness on pressure in the intercostal spaces which characterises pleurisy, but a sharp blow with the closed fist leads to wincing and usually grunting because of the concussion to which the diseased part is subjected. By increasing the force of such blows the deepest parts of the lungs may be tested, since in this way dullness due to consolidation of the deeper portions of the lungs may be detected even though the superficial investing parts are healthy.

The nature of the symptoms will vary according to the extent and character of the inflammation, from mild febrile reaction, with excited breathing and slight crepitation, to the more severe varieties in which the intensity of the symptoms are such as to threaten suffocation.

A marked feature of pneumonia in solipedes is that the patient obstinately stands in one position and never lies down so long as the severity of the inflammation lasts. The sharp crest on the lower border of his breast bone compels the horse to lie on his side, and since in this position the whole weight of the body has to be overcome in any full dilatation of the chest, he cannot retain the recumbent posture when any serious impediment to breathing exists. Hence it is that the fact of a horse suffering from pneumonia having lain down and remained so for some time is justly accepted as an indication of improvement.

Progress and results of the disease. The general symptoms above noted, remain with more or less intensity throughout. After the first flush of heat, on the occurrence of febrile reaction, the limbs become alternately hot and cold, and in this the general surface partakes to a less extent.

The tendency of pneumonia is to a crisis and recovery. Certain days have been supposed to be critical and on the whole the third, seventh, eleventh and fourteenth are those on which a favorable change is most probable.

Among the more favorable indications are the manifest abatement of the high bodily temperature and febrile symptoms generally, the increasing ease and regularity of the breathing, the greater force, distinctness and slowness of the pulse, the permanent return of warmth to the limbs, the softer and more elastic feeling of the skin, the recovery of appetite, and above all, the turning of the nose from the open window or the retention of the recumbent position for a length of time. These symptoms will become more patent day by day, and the absorption of the effused products and the clearing up of the lung may be traced by the gradually decreasing area of dullness and of the circular line of crepitation as ascertained by percussion and auscultation.

If on the contrary the disease takes an unfavorable turn, some such signs as the following will manifest it: Increasing rapidity and embarrassment of the breathing; smallness and indistinctness of the pulse, which is increased to perhaps 100 beats per minute; tumultuous heart’s action, the impulse of which is strongly felt behind the left elbow; a more laborious working of the flanks; frequent despondent looking toward the flanks; pawing with the fore feet, lying down, and as suddenly rising again; permanent coldness of the extremities; hanging head with great dullness and despondency of expression; dull, sunken, lusterless eye; hanging lower lip; leaden hue of the nasal mucous membrane; convulsive twitching of the muscles of the surface; reeling in gait, and extension of the crepitation over all the still pervious lung.

SUBACUTE PNEUMONIA. This term is employed to designate that subdued or milder form of the disease which sometimes arises spontaneously and at others follows the acute.

In this variety the characteristic symptoms may be much less marked and the disease is less easily recognized. There is some acceleration and quickness of pulse, lifting of the flanks and heat of the mouth and body generally. There are alternations of heat and cold of the surface and extremities, a rough, unthrifty coat, hidebound, a dull, listless moping manner and the same symptoms on auscultation and percussion as in the acute form.

The changes take place slowly but the disease may prove obstinate and is often followed by permanent alterations in the lungs. Rheumatic affections of the limbs, inflammation of the feet, and other diseases frequently supervene during the course of this form of the affection.