Part 25

=Left Side.= In the upper third a clear respiratory murmur is heard over the 8th, 9th and 10th ribs but is lost about the 11th. In the middle third the vesicular sound is feeble at the lower margin of the region and immediately behind the shoulder because of the proximity of the base of the heart. Towards the upper margin it is loud and harsh being complicated by the tubal sound. It is full and clear over the 7th rib whence it decreases in force to be lost at the 11th above and the 10th below. In the lower third the double heart beat is alone heard over the lower part of the 4th rib, the respiratory murmur reappears over the 5th and 6th whence it becomes weaker and is lost at the lower and upper margin of the region respectively over the 8th and 9th ribs.

=Right Side.= The sounds of the upper third simply repeat those of the left side. In the middle third the chief difference is the greater clearness and strength of the respiratory and tubal sounds immediately behind the shoulder. In the lower third a moderately strong respiratory murmur is rendered harsh by a tubal sound due to the proximity of the large bronchus going to the anterior lobe of the right lung. The respiratory murmur continues with diminishing force to be lost over the 8th and 9th ribs.

=Accidental but healthy Sounds.= These are more loud and frequent in the ox than in the horse. There is the same irregular rumbling and gurgling especially on the posterior parts of the chest. Gurgling as from a full bottle inverted is often clearly heard over the last six ribs on the left side, and appears due to the passage of liquids between the paunch and honey comb bag. An occasional sound as of water falling into an empty barrel is heard in the same region in cases of slight tympany and after saliva has been swallowed. Rumbling sounds are chiefly heard over the last ribs on the right side where the large and small intestines are situated. The superadded sounds in the ox are those of crepitation and friction. The crepitation or fine crackling due to a dryness of the areolar tissue under the skin is frequently present in oxen in average health. A fine crepitation is also heard on the left side from the bursting of myriads of minute bubbles of air generated among the contents of the paunch during the process of digestion. This is especially marked after the animal has fed on green food or potatoes. A loud friction or rubbing sound, which may be imitated by placing the back of one hand upon the ear and rubbing the palm of the opposite hand upon it, is likewise heard over the left side after eating. It is produced by the movements of the paunch during contraction and not being synchronous with the respiratory acts cannot be confounded with the friction sounds of pleurisy to be hereafter noticed.

=Sheep.= The diaphragm being attached to the last rib as in the horse the respiratory murmur may be heard to the second last. The shoulders being more movable than in the ox the anterior part of the chest can be more satisfactorily examined. The vesicular murmur is heard along the whole lower third on the left side though the heart sounds are superadded over the 4th, 5th and 6th ribs. Crepitation from the subcutaneous areolar tissue is rarely heard. Otherwise the sounds of the chest and abdomen correspond to those of the ox.

=Goat.= This animal differs from the sheep mainly in the greater force and clearness of the respiratory murmur.

=Pig.= It seems ridiculous to speak of auscultating the pig, yet he is sometimes thin enough and quiet enough to permit of one obtaining satisfactory results. Gentle treatment and scratching the back and abdomen will often persuade him to be temporarily quiet and docile. The vesicular murmur is very clear in the middle third of the chest on either side, but diminishes gradually on the last six ribs, and disappears on the second last. It is much less intense in the upper and lower thirds. In the posterior part of the chest rumbling and gurgling abdominal sounds are frequent.

=Dog.= The respiratory murmur is very clear over the whole chest. It is most intense along the middle third and becomes less clear on the 4 or 5 last intercostal spaces. The mobility of the shoulder permits an examination of nearly the entire chest. The respiratory murmur may be heard over the entire length of the lower third on the left side though the heart’s sounds are equally heard over the 4th, 5th and 6th ribs. Rumbling and gurgling abdominal sounds are much less frequent than in herbivora and omnivora.

=Birds.= The respiratory murmur is loud, clear and almost harsh on the sides of the thorax, beneath the wings, and considerably softer as heard on the back.

MORBID CHEST SOUNDS.

The close study of the healthy chest sounds upon the living animal is an essential prerequisite to the appreciation of the morbid. The abnormal noises are so varied, merge into each other by such imperceptible degrees, and so coexist and complicate each other that they often prove extremely puzzling to the unpractised ear. It is no more necessary that the musician should educate his ear to appreciate the most delicate gradations of musical notes, than that the auscultator should educate his in the sounds of the healthy and diseased chest. Written instructions are of about equal value in the two cases, they prove auxiliaries in the acquisition of knowledge but they can never supersede the practical study of the chest. A mere theoretical knowledge is too often useless in the presence of the patient.

The abnormal chest sounds are either modifications of those existing in health, or superadded sounds which have no counterpart in the healthy chest.

Modifications of healthy sounds. The =vesicular= or =respiratory murmur= may be =increased= or =diminished= in force or it may be entirely =absent=.

=Increase of the respiratory murmur=, is merely an increase in force without any modification in character and resembles juvenile respiration. If increased equally over the entire chest it is =general=, if only in a part it is =partial=. =General increase of the vesicular murmur= is heard after an animal has been submitted to moderate exertion for ten or fifteen minutes. In animals at rest it is heard in active fevers and in the symptomatic fever which attends acute inflammations.

=Partial increase= as for example in one lung only, or in circumscribed parts of both lungs, and especially along their superior borders, is indicative of disease of the lungs or the pleuræ. It testifies to the impermeability to air of some other portion of lung, from congestion, splenisation, hepatisation, plugging of a bronchial tube with tenacious mucous, tubercular deposits, tumors, emphysema, or hydrothorax. (See under these names.) The healthy portion of lung in such cases takes on the function of the whole, and the loud breathing is called =supplementary=.

=Diminution of the respiratory murmur=, like its =increase=, may be =partial= or =general=. =General diminution= is seen in anæmia, in low fevers, in all very prostrate conditions from the mere want of power to dilate the chest; in general emphysema (broken wind, heaves), in general miliary tubercular deposit in the lungs, or in that form in cattle in which the tubercle has been replaced by cretaceous deposits, from the animal’s inability to fully dilate the air cells; in enteritis, peritonitis and metritis the chest is more fully dilated because of the pain attendant on that act, and the breathing being short and quick the murmur is correspondingly low. In certain brain diseases with sluggish respiration the sound is equally feeble.

=Partial diminution of murmur= is more surely indicative of lung disease. It may arise from partial congestion when a supplementary murmur will be observable over other parts of the lungs, and a crepitant râle soon appears in the congested part; from local emphysema in which there is increased resonance in percussing the part; from tubercular or cretaceous deposit, when there will be exaggerated murmur elsewhere, or from bronchitis with blocking up of one or more small bronchial tubes and with louder respiratory sound in other parts.

=Absence of respiratory murmur= may be due to various causes, all of a diseased nature. Hepatisation of lung may be recognized when this condition is found associated with a crepitating râle around the margin of the silent part, and when percussion shows its solidity and want of resonance. Splenisation is associated with absence of respiratory sound and dullness on percussion, but no surrounding crepitation. Absence of sound in water in the chest is confined to the lower part of the chest, keeps the same level and ratio of increase in front and behind, and in the horse on the two sides, and has been preceded by the characteristic catching breathing and the friction sounds of pleurisy. Large tumors and extensive and circumscribed tubercular deposit will give rise to absence of sound over a limited area and plugging up of one or more bronchial tubes will lead to a similar result. Hepatisation of lung and water in the chest are, however, the common causes of loss of respiratory murmur.

The =bronchial or tubal sound= may be increased in pitch and in harshness in two conditions. 1st. In the early stages of bronchitis when the lining mucous membrane of the air passages is dry, thickened and inelastic. 2d. When that portion of lung intervening between one of the larger tubes and the surface of the chest is solid (hepatised) and thus proves a better conductor of sound than in the normal condition.

=Superadded abnormal sounds.= The =bronchial= sounds may be altered in their character so as to become =cavernous=, =amphoric= or =mucous= (rattling). The =cavernous= sound is usually caused by the presence in the lung of the cavity left after the discharge of an abscess or softened tubercle into a bronchial tube. It is thus preceded by cough and white, creamy discharge from the nose. If the discharge is fetid and grumous there has probably been circumscribed gangrene of the lung. An approximation to the sound may be produced by blowing into a widemouthed glass or porcelain vessel. The sound of =amphoric respiration= on the contrary is like that made by blowing into a narrow necked bottle. It is due to a similar cavity with a small orifice or to the existence of pneumothorax communicating by a narrow canal with a bronchial tube. It is rare in the lower animals, but Delafond mentions one case in the horse and two in dogs.

=Râles.= The remaining morbid sounds are known as râles, or rattles. They may either be referable to the bronchial tubes or the lung tissue. They are called dry or humid, according as they convey the idea of air drawn through a dry tube or one containing liquid.

The =dry râles= are due to narrowing of the bronchial tubes from the pressure of adjacent tumors, the thickening of the mucous membrane or the deposition on the surface of layers of tenacious mucus. The greater the narrowing the shriller the sound, and hence the distinction of bronchial râles into =sonorous= and =sibilant= (whistling).

The =sonorous râle= has been variously exemplified by the humming of a gnat, the cooing of a wood pigeon or the bass notes of a violin. It commonly bespeaks the onset of bronchitis and testifies to the thickened, dry and rigid character of the tubes, but may give place in as short a time as three hours to a mucous râle from the occurrence of a free secretion. It rarely extends over two or three days. Sometimes when caused by a piece of tenacious mucus obstructing a tube, it is very transient disappearing at once when the mucus is expelled by coughing. Sometimes it is modified by an occasional clicking sound from the flapping of a shred of semi-solid mucus attached to the walls of a bronchial tube. This disappears when breathing becomes more hurried.

The =sibilant= (whistling) =râle= often acknowledges the same causes as the sonorous, but indicates a narrower closure of the tubes. More frequently it is heard further back on the chest and results from pulmonary emphysema and dilatation of the smaller bronchial tubes (broken wind, heaves). It is then heard chiefly in expiration and coincidently with the second quick lifting of the flank. It is further associated with the double lifting of the flank in expiration with the short, weak, paroxysmal cough and the indigestion characteristic of broken wind. If the whistling noise is so loud as to be heard without applying the ear to the chest it is called wheezing.

A =mucous râle= is caused by air passing through any liquid contained in the bronchial tubes, such as mucus, pus, or blood. It may be imitated by blowing a large number of soap bubbles in a thick lather and noticing them burst simultaneously or successively. It is chiefly observed in bronchitis after the preliminary dry stage of the mucous membrane has passed off and an abundance of mucus has been secreted. The nature of the sound will vary according as it comes from the larger or the smaller tubes or in other words as to whether the bubbles are large or small. That from the smaller tubes is sometimes called a =submucous râle=. Either of these râles may be temporary or permanent as the mucus may be momentarily cleared away by coughing.

The =crepitant râle= is a sound of very fine crackling which has been variously compared to the crackling of salt when put on red hot coals, the noise of a sponge expanding in water and the rubbing of a small lock of hair between the finger and thumb close to the ear. The existence of the crepitant râle usually denotes the existence of the early stage of inflammation of the lungs, and the progress of hepatization in such cases may be traced by the advance of the line of crepitation which precedes it. So the progressive absorption of exuded matter in recover may be equally followed by a line of crepitation gradually decreasing in area until it meets in a point. The observations will be corroborated by the dull sound elicited on percussing the parts. The production of the sound has been attributed to the passage of air through the thick mucus in the smallest bronchial tubes or more plausibly to the separation of the walls of the air sacs and cells during inspiration, they having been previously adherent by reason of the secretions.

Crepitation is not heard in all pulmonary inflammations. In weak animals with a low type of inflammation tending to gangrene, and in those cases of broncho-pneumonia in which a viscid mucus blocks up the bronchial tubes passing to the affected lobes, it may be altogether absent.

Crepitation may further occur without inflammation. Thus in pulmonary œdema (dropsy of the lung) and capillary hemorrhage in which liquids are effused in the smaller bronchial tubes and air sacs a crepitation is sometimes heard.

A =modified crepitation= (=dry crepitant râle= of Delafond) is usually heard over an emphysematous lung. The noise in this case has been compared to that induced by handling a sheet of paper.