A series of 35 unselected cattle tested with synthetic medium tuberculin and synthetic medium johnin was subjected to post-mortem examination. In five instances (14·3 %) avian strains of full virulence for the usual experimental animals were recovered by the inoculation of guinea-pigs with glandular suspensions or by cultural methods used for the isolation of Johne's bacillus: in two of these cases an avian type was isolated from the glands of the alimentary tract and a bovine type from the thoracic glands. In addition there were five cases (14·3%) in which evidence of avian infection was not complete. From one a strain was obtained which was culturally identical with an avian type, but it was almost completely avirulent for laboratory animals. In two, acid-fast bacilli were seen in smears from the thoracic and mesenteric glands respectively, while in two, completely calcified glands were observed which were typically tuberculous, but were devoid of acid-fast bacilli (microscopical examination of smears and sections). Cultures from the organs of guinea-pigs inoculated with glandular suspensions from the four last-mentioned cases failed to grow tubercle bacilli. In these circumstances the evidence that the infection was of the avian type is largely presumptive, but the nature and extent of the lesions suggests that such may have been the case.

With, regard to the tuberculin and johnin tests, clear cut reactions to johnin were obtained in seven instances, a doubtful reaction in one and negative reactions in two. One-half of the animals were also positive to tuberculin.