682 INFECTI01T« DISEASES. 



In following up this fistula care must be taken not to injure the 

 facial artery, the facial vein, or Stenon's duct. Once the bone is 

 exposed the disease can be attacked in the depths. The diseased 

 interior is cut away by means of a special curette, all affected por- 

 tions being removed, and an iodine or iodoform dressing is then 

 applied. 



The operation is extremely troublesome, owing to the enormous 

 bleeding, and sometimes it is impossible to carry out successfully, 

 as in the case of old-standing and extensive lesions. To ensure 

 recovery under such circumstances, it is necessary to remove a por- 

 tion of the branch of the jaw, and this, though quite possible from 

 the scientific standpoint, would not be worth while in an animal, the 

 value of which is usually small. 



Curettage of the bone is only of value in dealing with recent 

 lesions, and even then should not be practised except in tlie case of 

 animals which the owners particularly desire to keep. 



In cases of actinomycosis of the upper jaw surgical treatment is 

 just as difficult as in the lower jaw, and calls for similar precautions. 



The diseased portions of bone having been removed, the cavity is 

 plugged with iodoform or cotton-wool, or a dressing saturated with 

 boric acid and iodoform. 



In all surgical operations it is important not to injure the dental 

 arteries or nerves, or the alveolo-dental periosteum. 



TUBERCULOSIS. 



Tuberculosis is a contagious disease produced by the action of 

 Koch's bacillus. It is common to man and all domesticated animals, 

 but it specially affects animals of the bovine species. Its existence 

 has long been recognised, although in oxen it was formerly con- 

 founded with the lesions of peri-pneumonia and echinococcosis. 



It was not until the beginning of the nineteenth century that 

 Laennec (1811) described the tuberculous lesion from the anato- 

 mical and pathological standpoint. Giirlt pointed out for the first 

 time in 1881 the similarity, the identity in fact, of tuberculous lesions 

 in man and the ox. 



In 1865 Villemin showed that tuberculosis could be conveyed 

 from animal to animal, always producing similar lesions, and in 

 1868 Chauveau proved that, in the calf, infection might arise simply 

 from the eating of tuberculous material. 



At a somewhat later date doubts were entertained regarding the 

 identity of human and bovine tuberculosis. Virchow denied the 

 identity of the two diseases on the basis of a comparative study of 

 the lesions. His opinion, however, has not prevailed, and the doctrine 



