In order to its production, however, it is necessary that the quantity of the liquid be limited. Generally, the lung must be moderately compressed, but not much flattened by the pressure. Hence the sound is heard, in the second stage of pleuritis or in hydrothorax, when the water is beginning to collect, and when it is nearly absorbed. Too small a quantity is not sufficient to afford the vibrations. Too much so compresses the lung that the air is prevented from sufficiently filling the bronchial tubes. If, however, the substance of the lung happens to be somewhat rigid and solid, in consequence of previous inflammation, so as to produce strong bronchial respiration, the egophony will continue, as the water increases, much longer than it otherwise would do. It may last even during the whole existence of the disease. Still it is, ordinarily, quite transitory, passing away in a few days. Egophony, when existing, if the patient sustains the upright posture, is most distinctly heard, posteriorly, near the lower margin of the scapula; but, with a change of position, there is a change in the audibleness of the sound, it being best heard about the upper portion of the liquid, except so far as obstacles to the conduction of the sound modify the result. CHAPTER X. RATIONAL SYMPTOMS. SECTION I. DYSPNEA. As diseases of the thorax, to a greater or less extent, affect the respiration, a few general remarks on the subject of dyspnoea are not inappropriate in this place. There are four circumstances, particularly, the existence of any one of which will disorder the respiration, unless its influence is by some means counterbalanced. These circumstances are certain disordered conditions of the blood, a deficiency in the quality or quantity of inspired air, a defect in the machinery designed to bring the blood and the air into contact, and a diseased state of the nerves, whose office is to invite to action the muscles of respiration. To some extent there may be a balance of influences. For instance, the distress which would otherwise arise from a deficiency in the quality of air allowed to enter the lungs, may be prevented by such a diminution of nervous' sensibility as renders the patient insensible to the want experienced. Dr. C. J. B. Williams has given us the following table, showing what he calls "the proximate causes of dyspnoea." The table is very accurate and appropriate; though not being founded directly on the circumstances which I have named as remote causes, the classification is not what those circumstances would directly suggest. I would here remark that the original import of the term, dyspnea, is difficult breathing, and Dr. Williams has here used it in a sense so extensive as to embrace the slow labored respiration of coma, though it is ordinarily limited to what is hurried and distressing, and it is in this sense, mainly, that it is concerned with diseases of the thorax. 1. BY IMPEDING THE ACCESS OF PURE AIR TO THE LUNGS. a. Mechanical. Rigidity of parts of the respiratory machine: e.g. Ossification of cartilages; induration of the pleura; rickety distortions. Pressure on ditto : e.g. Tumors or dropsies of the abdomen. Obstructions of the air-tubes : e.g. Effusions in, swellings of, tumors pressing on, the air-tubes; Spasm of the glottis; spasm of the bronchi. Compression of the lungs : e.g. Effusions or tumors in pleural sac; c. Vital. Pain of parts moved in respiration : e.g. Pleurodynia; pleuritis; peritonitis, &c. Paralysis of muscles of respiration : e.g. Injuries of the spinal marrow on the neck, &c. Weakness of ditto : e.g. Excessive prostration, from åtaxic fevers, &c. Spasm of ditto : e.g. Tetanus; spasmodic asthma, &c. 2. BY THE STATE OF THE BLOOD. a. Mechanical. Obstruction to the passage of the blood: e.g. Diseases of the heart and great vessels; tumors pressing on them. b. Chemical. An excessively venous state : e.g. Violent exertion; idiopathic dyspnoea (?) Deficiency of red particles : e.g. Anæmia; cholorosis. 3. BY THE NERVOUS RELATIONS OF RESPIRATION. Excessive sensibility of the par vagum : e.g. Hysteric dyspnoea; cerebral fevers; neuralgia (?)` Defective ditto: e.g. Coma: narcotism, &c. (breathing slow.) The standard of healthy respiration, in an adult, is not far from sixteen breaths in a minute, though it may range from twelve to twenty, consistently with the existence of comfortable health. Disease, especially inflammation of the lungs and the pleura, may increase the respirations to thirty or forty per minute, and violent disease may raise them as high as even sixty or seventy. In children, the respiration, both in health and in disease, is more rapid in the increase ratio of age; and, in general, with females it is rather quicker than with males. In acute affections, the degrees of dyspnoea is usually not far from proportionate to the extent of the disease. In chronic cases, however, it is quite otherwise. The nervous irritability may gradually be so deadened, and the functions of the system so accommodated to the depressing influence, that there shall be but little variation in the respiration, even though there is a great Ideal of thoracic disease. On the contrary, the nervous irritability may become so exalted as to quicken the respiration and alarm the patient with a sense of dyspnea, when the existing organic disease is but trifling. Still farther, there may be a hurried respira tion without the patient's being sensible enough to perceive it; or, on the other hand, a respiration scarcely quickened, while he anxiously imagines the existence of serious respiratory disturbance. There are other modifications of the respiration, caused particularly by peculiarities of nervous influence; -such as the suspicious breathing, or the taking now and then of a sigh or deep breath, and comatose breathing, or a slow and struggling effort of vitality to sustain the respiratory process. The true nature of these conditions I design to illustrate in another volume. The knowledge of their pathology is not necessary to a practical understanding of the subject on which I propose now to treat. SECTION II. COUGH. A cough is so common an attendant of diseases of the thorax, that a few general remarks on the subject are here not out of place. It may be defined to be an abrupt or convulsive expiration or series of expirations, in which there is a continuation of the glottis, trachea, and larger bronchial tubes. When several expirations constitute the series, this is immediately succeeded by a loud and forcible inspiration, which, in its most marked form, constitutes what is commonly called a whoop. Coughs have many varieties of character, some of which are expressed by the phrases a short, dry or hacking cough, a nervous cough, a sonorous cough, a suppressed cough, a stridulous cough, a loose cough, a hollow cough, a spasmodic cough. These terms, which sufficiently explain themselves, are not separately characteristic of particular diseases; as the same form may arise from different diseases, and different forms from the same disease. Indeed, so indefinite are the shades of character which a cough assumes, that its various phases cannot easily be described. Again, coughs may be classed according to their exciting causes. These are various, but may be divided into two general classes, the existence of some irritating substance within the air-tubes, and a morbid irritability of the sentient portions of those tubes, or some portion of the respiratory apparatus. The cough, in the first instance, may be called excretory; and in the second, irritative. The design, or as logicians say, the final cause of the excretory cough, is to eject the offending matter or exciting cause. Of course the effect of agents tending to suppress it is injurious; and the object of remedial means should be to assist nature to remove that which creates the irritation, even though, as is sometimes the case, the cough be thereby increased. The irritative cough proceeds from causes which are governed by a general law in the animal economy, and has no immediate design or final cause. Its tendency is only injurious; and the object of medication should be to suppress it, by subduing the excessive irritability. But these classes of coughs, however, may be, and often are, united; in other words, the cough partakes, in part, of each character. Of course, the treatment should have in view a twofold object. The excretory cough may be produced by the existence of a foreign body in a portion of the air-tubes. For example, a person incautiously allows a portion of food or drink to enter the glottis. This suddenly developes a cough, the violence of which will be proportioned in part to the irritating nature of the substance. The effect of any thing highly stimulating, like vinegar or pepper, will be more severe than that of simple water or bland food. The diseases which mostly create this class of coughs are affections of the mucous membrane of the air-tubes and of the parenchyma of the lungs, which is in juxtaposition with this membrane. In these diseases, the cough will be more or less teasing or tickling, according to the character of the excreted matter in the tubes. A strong saline excretion may produce a loud sonorous cough; whereas thick mucous, or pus, or blood, with little chemical power, will only create a mild, though, perhaps, frequent mucous cough. In most cases of bronchitis and pneumonitis, however, the cough is more or less mixed, and not purely of the excretory kind. In regard to the irritative cough, there may be an increased sensibility of the tubes resulting from local inflammation. In bronchitis, the mucous membrane of the bronchi is inflamed, and the morbid irritation is the result. This, in the first stage of the |