258 TUBERCULOSIS 



infect the pharyngeal lymphoid tissue, tonsils, etc., tubercular 

 lesions of these parts being much more frequent than was 

 formerly supposed. Thence the cervical lymphatic glands may 

 become infected, and afterwards other groups of glands, bones, 

 or joints, and internal organs. 



The Toxins of the Tubercle Bacillus. Two outstanding 

 features of the action of the tubercle bacillus are the occurrence 

 of necrosis in the cells of tubercle nodules and the production 

 of general disturbances of metabolism accompanied by fever. 

 It is natural to refer these phenomena to the effects of toxins 

 formed by the organism. The study of such toxins centres 

 round the substance known as tuberculin which Koch brought 

 forward in 1890-1 as a curative agent for tubercular affections. 



Koch's Tuberculin. Koch stated that if in a guinea-pig 

 suffering from the effects of a subcutaneous inoculation with 

 tubercle bacilli, a second subcutaneous inoculation of tubercle 

 bacilli was practised in another part of the body, superficial 

 ulceration occurred in the primary tubercular nodule, the wound 

 healed, and the animal did not succumb to tuberculosis. This 

 reaction was further studied by means of tuberculin, which 

 consisted of a concentrated glycerin bouillon culture of tubercle 

 in which the bacilli had been killed by heat. Its essential 

 components probably were the dead and often macerated bacilli 

 and the substances indestructible by boiling which existed in 

 these bacilli, or which were formed during their growth. The 

 injection of '25 c.c. of tuberculin into a healthy man causes, in 

 from three to four hours, malaise, tendency to cough, laboured 

 breathing, and moderate pyrexia ; all of which pass off in 

 twenty-four hours. The injection (the site of the injection being 

 quite unimportant), however, of '01 c.c. into a tubercular person 

 gives rise to similar symptoms, but in a much more aggravated 

 form, and in addition there occurs around any tubercular focus 

 great inflammatory reaction, resulting in necrosis and a casting 

 off of the tubercular mass, when this is possible, as for instance 

 in the case of lupus. The bacilli are, it was shown, not killed in 

 the process. 



Koch's theory of the action of the substance was that the tubercle 

 bacillus ordinarily secretes a body having a necrotic action on the tissues. 

 When this is injected into a tubercular patient, the proportion present 

 round a tubercular focus is suddenly increased, inflammatory reaction 

 takes place around, and necrosis of the spreading margin occurs very 

 rapidly, the material containing the living or dead bacilli being thrown 

 off en masse instead of being disintegrated piecemeal. It appears, 

 however, that this explanation may not be the true one ; for, on the one 

 hand, other substances besides products of the tubercle bacillus may 



