162 MICRO-ORGANISMS AND DISEASE. [CHAP. 



material, as vegetable and animal decaying matter, and since 

 free access of air is always insured they will eventually form 

 spores. Such soils, owing to the presence of these spores, 

 will remain a permanent source of infection to sheep and 

 cattle sojourning on them (Koch). 



(m) Bacillus tuberculosis (Koch). In all cases of tubercu- 

 losis in man, cattle (Perlsucht) and monkeys, of tuberculosis 



FIG. 88. FROM A PREPARATION OF HUMAN TUBERCULOUS SPUTUM, STAINED 



AFTER THE EHRLICH-WEIGERT METHOD. 

 The nuclei are stained blue, the tubercle-bacilli pink. Magnifying power 700. 



artificially produced (by inoculation with human or bovine 

 tuberculous matter) in cats, guinea-pigs, rabbits, and rats, and 

 in spontaneous tuberculosis in birds (hens), Koch J found in 

 the fresh state, and particularly after staining with methylene- 

 blue and vesuvin, peculiar fine bacilli, some with bright oval 

 spores, some without, some smooth and homogeneous - 

 looking, others more of a beaded appearance. One cubic 

 1 Berliner klin. Wochenschrift, xv. 1882. 



