Whilst many of these anatomical changes are fortunately remediable, others are not so, and the efforts of the practitioner can only be directed to the relief of their symptoms, or, more correctly, their effects. Amongst these, disturbances of respiration, spasm, cough, expectoration, vomiting, and pain, alone require to be briefly noticed here.

Dyspnoea is a natural effort to increase oxygenation, and is due to stimulation of the respiratory centre in two distinct ways, viz. (1) by the imperfectly oxygenated blood circulating within it, and (2) by exaggeration of the impressions coming from the air passages and lungs. Obviously these two sets of causes are usually combined, since such anatomical changes as have been mentioned, interfere at the same time with the proper contact of the air and blood in the lungs, and irritate the pulmonary branches of the vagus. As a rule, dyspnoea is successful and highly beneficial; but unfortunately, if it fail to give relief, it tends to aggravate the distress.

Spasmodic dyspnoea, commonly called "asthma," is referable to sudden intermittent irritation of the vagus or centre.

Powerful reflex respiratory impulses are thus generated, and pass out to the bronchial muscles and the diaphragm, which are spasmodically contracted, interfering with the entrance of air.

Cough is essentially a physiological act, in itself highly beneficial, which may require to he encouraged and increased. Much more commonly, however, it is excessive, and becomes one of the most distressing symptoms demanding relief in disease of the chest. Expectoration may also be considered physiological within certain limits, but will require to be modified therapeutically when the quantity of the sputa is either excessive or deficient, or the quality rendered morbid by inspis-sation or decomposition. Vomiting is closely associated with cough and expectoration, which is not a remarkable circumstance, the two acts and their mechanisms being nearly allied to each other, as we saw in chapter iv (Emetics And Vomiting).

Pains, and sensations of irritation, tickling, necessity to cough, "want of breath," tightness, oppression, suffocation, etc., are always exceedingly distressing; and, as they are among the chief complaints of patients, demand relief if it can be afforded.

IV. Natural Recovery

Nature's method of meeting an extraordinary or otherwise morbid influence by destroying or removing it, is well seen in the case of the respiratory system. Coughing and sneezing are provisions for expelling any obstructing or irritating mass from the air-passages; and although apparently but of little service in preventing the most serious kinds of lung disease, they may really expel infective and other causes of morbid change much more frequently than we suspect, just as they guard the nose and the glottis from mechanically irritant particles.

The second great natural method of relief which is seen at work in this system is reaction or counter-action. The respiratory muscles respond to an obstruction in the passages by such an increase of the force and frequency of their contraction as will negative its action, and after a time they become hyper-trophied if the obstruction persist. Dyspnoea or (better) hyperpnoea, is- the result, a large reserve of muscular force and an almost unlimited power of hypertrophy sufficiently compensating for the diminished size of the air-passages and air-current, by increasing the depth and the frequency of breathing. The same principle is at work in the catarrh, that is the hyperaemia and secretion, set up in the air-passages or lungs on the entrance of a foreign body; the mucous, serous, or even purulent discharge-all evidences of different degrees of reaction-being essentially intended to counteract the irritant, as well as to carry it off and repair the damage it may have wrought.

The third natural provision against a morbid influence is the removal of its effects, whether the influence itself have been removed or antagonised, or not. Thus excessive secretions or other products of disease, which may in turn cause fresh obstruction of the passages, are removed by cough, expectoration, and vomiting; and the venosity of the blood which they cause is dispelled by hyperpnoea. Even spasm of the bronchi probably never causes death, because removed by the carbonic acid which accumulates in the blood in the second stage of asphyxia. Haemorrhage from the lungs or nose frequently comes to the relief of over-distended veins, and removes the most urgent symptoms.

Vicarious action is yet another method of natural relief, of which abundant advantage is taken in respiratory disease; extraordinary muscles being called into play in hyperpnoea, the healthy parts of the pulmonary substance taking on increased function, and the skin and kidneys doubtless becoming more active as excretory organs.

In these several ways nature will frequently afford relief of respiratory disorders and diseases, whilst the cause of them is still at work, by removing or counteracting it and its effects. If she fail, and disease is established, recovery may still follow artificial treatment, the proper province of which is thus to assist, not to compel, much less to thwart nature. Even if organic changes have occurred, recovery may be effected by repair, as we see in inflammation of the lungs and pleura.