TUBERCULOSIS. 317 



bacilli from place to place phagocytes are not always 

 necessary, for the bacilli seem capable of transportation 

 by streams of lymph alone. 



Notwithstanding the steady advance which takes place 

 in most observed cases of tuberculosis, and the thoroughly 

 comprehensible microscopic explanation of it, many cases 

 of tuberculosis recover. 



The periphery of every tubercle is a zone of reac- 

 tion, with a tendency to granulation and organization. 

 If the vital condition is such that through inappro- 

 priate nutriment or through unusually active phago- 

 cytosis the activity of the bacilli is checked or their 

 death brought about, this tendency to cicatrization is 

 allowed to progress unmolested, and the necrosed mass 

 becomes surrounded by a zone of newly-formed contracting 

 fibrillar tissue, by which it is perfectly isolated. In such 

 isolated masses lime-salts are commonly deposited. Some- 

 times this process is perfected without the destruction of 

 the bacilli, but with their incarceration and inhibition. 

 Such a condition is called latent tuberculosis, and may at 

 any time be the starting-point of a new infection and lead 

 to a fatal termination. 



In 1890, Koch ! announced some observations upon the 

 toxic products of the tubercle bacillus and their relation 

 to the diagnosis and treatment of tuberculosis, which at 

 once aroused an enormous, but, unfortunately, a transitory 

 enthusiasm. 



These observations, however, are of capital importance. 

 Koch observed that when guinea-pigs are inoculated 

 with a mixture containing tubercle bacilli the wound 

 ordinarily heals readily, and soon all signs of local dis- 

 turbance other than enlargement of the lymphatic glands 

 of the neighborhood disappear. In about two weeks there 

 occurs at the point of inoculation a slight induration which 

 develops into a hard nodule, then ulcerates, and remains 

 until the death of the animal. If, however, in the course 

 of a short time the animals are reinoculated, the course 



1 Deutsche med. IVochemchrift, 1891, No. 343. 



