Consumption was once thought to be both an incurable and an unpreventable disease. It came mysteriously; it often attacked the youngest and the fairest; it destroyed promising careers; and unless it could be checked by the exile of the patient to a warmer climate than England, its cure was thought to be hopeless, and death sooner or later inevitable. Of late years some considerable progress has been made in respect both to its prevention and to its successful treatment. The disease has by the researches of Koch been shown to be due to the ravages of a minute bacillus in the tissues. The effort of medicine in the treatment of consumption is first to make the tissues resistant, and next to cut short the life of the bacilli or to limit their power for evil. This end is mainly accomplished by the following means - giving the patient sunlight and fresh air, regulating the diet, next by the application of antisepsis. The tubercle bacillus. - Before proceeding to point out how these objects can be attempted, I will describe the appearance and life history of the tubercle bacillus. If a beam of sunlight fall through a chink of a shutter into a darkened room, a number of motes will be seen to be floating about in it. These motes, made visible by the strong light, are present everywhere in the atmosphere in countless numbers. If they be allowed to settle and are examined under a microscope, it will be seen that they are composed of particles of dust and of minute rod-like bodies or bacilli. These bacilli, though simple in structure and closely resembling one another in shape, are yet so dissimilar in their action and life that they require certain soils and certain conditions in order to grow and multiply. It is probable that the tubercle bacillus, pictured in Fig. 11 is very largely distributed in the atmosphere; and if taken in with the breath it may settle on and grow in the lungs, and produce phthisis or consumption. If taken with the food it may settle and grow in the intestines and produce consumption of the bowels; if introduced into the brain it may cause tubercular meningitis, and if it finds its way into the marrow of the bones it may cause abscesses of them. In order, however, to grow in the human body the tubercle bacillus must find the right soil, exactly in the same way as a seed will not sprout unless it falls on the right soil. The conditions which produce in the tissues of the lungs or elsewhere, the nidus or soil proper for the growth and development of the tubercle bacillus, are probably in some measure hereditary, and also largely due to environment. The rebreathing of expired air, damp conditions of soil and defective nutrition may be set down as predisposing causes. Why one person should contract consumption and another should not is not fully known. Once, however, the tubercle bacillus is established in the tissues of the air vessels of the lungs, it undergoes rapid multiplication. By its irritating presence inflammation is set up, the tissue breaks down into pus, and cavities are ultimately formed in the lung. The patient becomes emaciated, loses strength, and finally dies from exhaustion or from insufficient aeration of the blood, owing to the fact that a large part of the lung has broken down and has been spit up in coughing.

The aims of treatment in pulmonary consumption are to improve the health and render "the soil" for the bacillus more resistant, to combat and conquer the bacillus, to deprive it of its proper nutriment, and, if unable to kill it outright, to render it weak and powerless to work mischief. It is, unfortunately, not yet known positively what substances are destructive of the life of the tubercle bacillus, but there is some reason to believe that oil and soda salts are antagonistic to its life. Hence probably the well-known benefits which result from the use of cod-liver oil. How the oil acts is by no means clear. The opinion of Hughes Bennett, by whom its use was introduced, was that it prolonged life by improving the nutrition of the tissues. It is now suggested by others that the oil, by being burnt up in the body, absorbs the oxygen required for the active multiplication of the micro-organisms. What we do know, however, is, that if wasting can be checked, and the weight of the patient increased, the tubercle bacillus is often successfully combated.