Diffuse tubercle tissue usually results from a rather extensive local infection resulting in many small foci near together. From these tubercles start to grow, and these coalescing form consid erable areas of tubercle tissue. In addition to the formation of tubercles the bacilli o• the pres ence of the tubercle tissue may set up secondary inflammatory processes.
Suppuration in connection with tubercular in flammation frequently occurs. In the so-called `cold abscess,' however, the fluid is not, properly speaking, pus, but the products of breaking down of the tubercles. The question as to whether the tuberele bacillus alone is capable of causing sup puration is still debated. It seems probable, however, that most eases of suppuration in tuber cular conditions are due to «•hat is known as `mixed infection,' that is, the presence of pyo genie cocci with the tubercle bacilli.
Acute general miliary tuberculosis is charac terized by a rapid development of tubercle?, ally of small size. in many parts of the body at about the same time. The number of tubercles is frequently very large. One of the explanations offered for such sudden general diffusion of tu bercles is that the infection is secondary to tuber cles located in the walls of some of the small blood vessels or lymphatics.
Pulmonary tuberculosis. tuberculosis of the lungs. lung consumption, o•, most commonly called simply 'consumption.' is a form of tuber cular infection in which the only or the most prominent lesions are in the lungs. The bacilli usually gain entrance by being taken into the lungs with the inspired air. Less commonly in
fection of the lung may occur through bacteria being brought to them by means of the blood or lymph channels front tubercular foci in other parts of the body. Several factors must be con sidered as determining the character of the in flammation which the tubercle bacillus may induce in the lungs. Among theAc may bo men tioned the number of bacilli introduced, their virulence, the manner in which they enter the lungs, whether in respiration or by means of the blood or lymph, the susceptibility of the indi vidual, etc. As a result of variation in these factors we find a variation in the character of the inthonmation set up. Thus there may result an exudative inflammation in which the air spaces of the lung and the smaller bronchi are filled with serum, lencocytes, fibrin, and cast-off epi thelium. Such reaction is quite similar to that induced by the pneumococcus in pneumonia. On the other hand, instead of an exudative inflamma tion, the tubercle bacillus may bring about the production of new tissue, that is a productive inflammation. This new tissue is composed of small round cells and epithelioid cells, such as hove been described above as tubercle tissue. In some eases there is death or necrosis of lung tis sue with the formation of abscesses.
While it is common for these different lung tissue reactions to tubercular infection to be as sociated, the predominance of one or another allows us to differentiate several quite distinct types of tuberculosis of the lungs.