ECONOMIC IMPORTANCE AND ETIOLOGY 17 



Liverpool in 1906, English veterinary surgeons at once 

 recognized it as occurring in their experience. 



Although Johne and Frothingham first observed the 

 bacilli in 1895, they regarded them as tubercle bacilli in 

 a modified form, and their opinion was upheld until 

 1906, v^^hen B. Bang proved the condition to be distinct 

 from tuberculosis. He was able to reproduce the 

 disease in calves by feeding them with large quantities 

 of infected intestine; and Miessner and Trapp and 

 Malm have confirmed his results. 



In 1910 the present writers prepared a medium on 

 vv^hich the bacillus was grown, and in the following 

 year showed that the cultures fulfilled Koch's postu- 

 lates; thus the undoubted relation of the bacillus to 

 the disease was proved. For fuller details of this 

 work, and a description of the morphology of the 

 bacillus, the reader is referred to Chapter VI. 



In the later stages of the disease the bacilli are 

 discharged in large numbers in the faeces of the 

 animal; and it is with these bacilli that the food 

 supply and water become infected and the disease 

 conveyed to other animals. There is now no doubt 

 that the disease is not confined to cattle, but may 

 attack sheep, deer, goats, and possibly allied animals. 

 It occurs in animals of both sexes and all ages ; though, 

 from its chronicity, it is never observed in the very 

 young. As has already been pointed out, a damp, 

 marshy district seems to predispose to infection, 

 possibly by allowing the specific bacillus to retain its 

 vitality for a longer period outside the animal body. 



The length of time the bacillus can live and remain 

 infective outside the body has not been accurately 

 determined, but it is probably very considerable. 

 Although it is highly improbable that the bacillus can 

 multiply in soil, it is quite conceivable that dung, 



