152 THE MORE CHRONIC INFECTIOUS DISEASES 



Toxins. The peculiar evidences of tuberculosis are 

 due to the toxins elaborated by the causative germ, 

 which are both extracellular and endotoxic. The former 

 produce the constitutional symptoms of fever and 

 general depression of health. They are also probably 

 responsible for some of the inflammation in the neigh- 

 borhood of tubercles. The endotoxins, on the other 

 hand, produce the peculiar local inflammation called 

 the tubercle, and cause its degeneration into caseous 

 material. During an infection with tuberculosis there 

 will be developed in the body fluids a very slight 

 amount of substance as antibody to these endo- and 

 extracellular poisons. It is of little importance in 

 the diagnosis, treatment, or protection of the indi- 

 vidual, and a specific resistance to tuberculosis is not 

 acquired by passing through an attack. Recbvery 

 ensues when the health of the individual and his tissues 

 is strong enough to inhibit the multiplication of bacilli. 

 A lighting up of the disease may occur when the resist- 

 ance weakens by reason of some acute disease, bad 

 habits, and the like. 



Predisposing Causes and Transmission. Tuberculosis 

 spares no walk of life, but is more common where the 

 lack of body care reduces resistance. It is preeminently 

 the disease of crowded, dark, illy ventilated, badly 

 drained tenements. It comes in the pulmonary form 

 frequently, as an infection on top of an acute cold. 

 The disease is spread in by far the largest percentage 

 of cases by the direct inhalation of germs coughed out 

 by a tuberculous person and contained in dust con- 

 taminated by tuberculous sputum. The sputum must, 

 of course, dry before it is pulverized into dust by walk- 



