TUBERCULOSIS OF THE LUNGS (CONSUMPTION).—With its con ception of " pulmonary tuberculosis," public opinion generally associates the idea that in this disease the affected organ, the lung, gradually wastes away and finally breaks up. This assumption is true only in some cases of the disease. Under the name " pulmonary tuberculosis " are included only those affections of the lungs which are brought about by the action of the tubercle-bacillus. This infinitely small micro-organism was demon strated by Robert Koch, in 1882, to be the cause of tuberculosis. It can be seen only when magnified many hundred times under the microscope (see Fig. 62).
As a result of infection by the tubercle-bacillus, a great many changes may take place in the lung. These changes will vary according to the number of these organisms that enter the lung, according to the avenue of infection, according to the age and constitution of the patient, and according to other, partly unknown, conditions on the part of the body and of the bacillus. Only the more important forms of the disease can be considered here.
Pulmonary tuberculosis is a pronouncedly infectious disease. Every case must be preceded by the entrance of the tubercle-bacillus. The con ditions, however, are not such that every invasion of disease-germs is bound to be at once followed by an outbreak of tuberculosis. The healthy human body is fortunately able, as a rule, by aid of its natural resistance, to with stand the action of the bacillus. Not until the body has lost this natural bulwark—either as a result of some severe general disease, or by reason of an excessive loss of blood or body fluids, or, principally, by harmful influences constantly affecting the lung—are the tubercle-bacilli able to gain a foothold and develop without hindrance.
The of the heredity of consumption requires some consideration. It has been scientifically demonstrated, in an exceedingly small number of cases only, that children have been born affected with tuberculosis. As a rule consumption is, even during the first weeks of life, the result of an infection from tuberculous members of the family. That which in reality may be directly transmitted from parent to child is a general constitutional weakness, a decreased power of resistance, the nature of which is not well understood. This tendency or predisposition of one person to succumb to
morbid influences more readily than does the average person—to be almost defenceless, especially against the action of the tubercle-bacillus—manifests itself, even in early childhood, by a series of changes known as scrofulous. Later in life, the so-called " consumptive habit " of the body may be present. This is shown by a rank growth of the body, a lank and lean figure, flattened chest, stooping posture, protruding cheek-bones, prominent shoulder-blades, hanging shoulders which are moved slightly forward, and a pale and sallow complexion (see Plate XVII., Fig. 2).
The chief avenue of entrance of the infection is by the inhaled air. The bacillus is contained in the sputum or some other secretion of a tuberculous patient ; and when this secretion is allowed to dry, the bacilli are set free, are mixed with the dust, and inhaled with the air. The extremely fine vapour which, on coughing or hawking, is emitted to a distance of a yard or more, remaining suspended in the air for some time, may likewise contain tubercle bacilli, which may transmit infection by inhalation. Direct infection is possible also through kissing tuberculous persons, or even through the medium of their hands, which may be soiled by wiping and drying their lips. Danger of infection may follow the ingestion of the products of tuberculous animals. Milk, especially, has been found to contain tubercle-bacilli, even though the cow did not suffer from tuberculosis of the udder, but from a tuberculous affection of some internal organ.
Among the causes which weaken the body, or impair the respiratory organs, thus preparing the soil for the colonisation of tubercle-bacilli, the following are the most important : Deficient nourishment, unfavourable conditions of dwellings, too early resumption of work after severe diseases, alcoholism, injurious attitude of the body when working, and constant inhalation of irritating dust. In women, frequent confinements are an additional factor. It is also of importance to remember that tuberculosis often follows measles, whooping-cough, and pneumonia.