356 MANUAL OF BACTERIOLOGY. 



than tuberculosis in a very large proportion of cases. Indeed, 

 the statement is made by competent authorities that nearly 

 all persons above the age of i8 years probably have latent 

 tuberculous foci in their bodies.* 



In nearly every case which comes to autopsy, whether the 

 subject showed evidence of tuberculosis during life or no, 

 tubercle bacilli may be found in the lymph-glands, if not 

 directly with the microscope at least by the inoculation of 

 susceptible animals with bit of the gland. In this way as 

 many as 90 per cent, and over of autopsies in hospitals have 

 revealed the presence of tubercle bacilli whether there were 

 lesions of tuberculosis or no lesions of tuberculosis. The 

 feces of persons who are suffering from pulmonary tuberculosis 

 may contain the bacilli even in cases in which there is no 

 involvement of the intestine. In such cases the bacilli are 

 swallowed with the sputum, and are discharged from the 

 intestines. 



In external nature the tubercle bacillus is found for the most 

 part in the air surrounding tuberculous patients. They are 

 found not only in the dry air attached to floating particles, 

 but Fliigge has shown that they are thrown into the air by 

 tuberculous persons in every act of coughing, and that they 

 remain for a long time floating about on the little globules of 

 sputum. 



The lesion produced by the tubercle bacilli in the tissues 

 of men and the lower animals is called a tubercle, which in 

 the beginning is a grayish-white area about the size of a 

 millet-seed. In sections of the tissue young tubercles are 

 found to present several different structures. Near the 

 center, one or more very large cells called giant-cells occur. 

 They contain several or many nuclei which are frequently 

 arranged in a crescentic manner at one side of the cell. Tuber- 

 cle bacilli can sometimes be demonstrated inside of the giant- 



*Gunther. hoc. cit. p. 472. 



