SYMPTOMS AND DIAGNOSIS 39 



part of the large intestine may show enormous numbers 

 of bacilH, yet the disease may not extend to such parts 

 of the bowel as are within reach of an arm or of a 

 curette. This is well illustrated in the graphic records 

 of the comparative numbers of bacilli in scrapings 

 taken from the mucosa of each lo feet of the in- 

 testines of cattle killed while suffering from Johne's 

 disease, drawn up by M'Fadyean, Sheather, and 

 Edwards. These authors' results show that by far 

 the largest number of acid-fast bacilli are found in the 

 neighbourhood of the ileo-caecal valve, and that the 

 number falls off almost to nil after the rectum is 

 reached, though in some cases films from rectal 

 scrapings are very rich in acid-fast bacilli. This 

 agrees with the experience of the present writers. 



For these reasons the examination of scrapings from 

 the rectum cannot be relied upon, and a negative result 

 is valueless. Reichel and Deubler, as the result of an 

 examination for tubercle bacilli in the faeces of bovines 

 suffering from tuberculosis, arrived at the following 

 conclusion : Microscopical examination of faeces and 

 rectal scrapings is of no value, on account of the 

 frequent presence of bacilli with the morphological 

 and staining characters of the tubercle bacillus, but 

 which are not tubercle bacilli. 



The problem of obtaining a reliable method of diag- 

 nosis was nearer solution when O. Bang, in 1909, 

 found that a certain proportion of cattle suffering 

 from Johne's disease reacted to avian tuberculin, in 

 the same way that tubercular cattle react to ordinary 

 tuberculin. In the absence of an autogenous vaccine, 

 which it was impossible to obtain until the specific 

 bacillus had been cultivated outside the animal body, 

 O. Bang's reagent was the best so far obtained ; but in 

 the hands of English users, and in our own experience. 



