199 



Tuberculosis sputum reduced to dust and inhaled by animals 

 causes tuberculosis, and a much less amount is necessary to pro- 

 duce the disease by inhalation than by ingestion, though infec- 

 tion by ingestion is believed to be more common than is generally 

 supposed. 



It is next pointed out that a decrease in the number of cases 

 of tuberculosis can, in many places, be correlated with an im- 

 provement of the water supply. It is reported that tubercle bacilli 

 live for several months to more than a year in water and other 

 material. 



As regards the exact time that tubercle bacilli live under cer- 

 tain conditions of environment, it was found that whereas pure 

 cultures of non-spore-bearing organisms and the vegetative cells 

 of spore-bearing germs exposed to direct sunlight in thin smears 

 were killed in half to six minutes, the human, bovine and avian 

 types of tubercle bacilli exposed in the same way were killed in 

 one to four minutes. 



The former group of organisms exposed to desiccation in the 

 dark died in one to four days, spores of B. subtilus took thirty-five 

 days ; the tubercle bacilli, four to eight days. 



Pure cultures of bovine tubercle bacillus mixed in cow manure 

 and exposed in a 2-inch layer in a pasture field in the sunshine re- 

 mained alive and virulent for two months. Guinea pigs inocu- 

 lated with germs exposed in manure in the shade developed the 

 disease with greater severity than those animals which were inoc- 

 ulated with germs not protected from the sun. 



Tubercle bacilli in the manure of a naturally infected cow, ex- 

 posed in the same manner as the artificially infected manure, were 

 dead within two weeks after exposure, whilst those bacteria in 

 garden soil and in a dead tuberculosis guinea pig buried in garden 

 soil were alive on the 213th and 71st days, respectively, and dead 

 on the 230th and 99th days, after first exposed. 



Tubercle bacilli live for more than a year in running water. A 

 watering trough harboring these germs may therefore be a dan- 

 gerous source of infection to cattle. 



Another possible source of infection is the bones of tuberculous 

 animals which have been ground and utilized for manurial pur- 

 poses. The danger from this source would, however, be obviated 

 if the bones were steamed as is frequently done. — Agricultural 

 Neivs. 



