The occurrence of tuberculosis of bovine origin in man to an extent of practical importance is, as people have seen, denied by Koch and those who agree with him. Virulence necessarily declines with prolonged cultivation, and bacilli may assume slightly different forms on different culture media. According to Von Behring and De Jong passage through goats is able to change the bacillus of the typus humanus into the typus bovinus. Von Behring's Views as to human tuberculosis. He holds that bovine tubercle bacilli, after long residence in human tissues from infancy onwards, become the source of adult phthisis, the chief cause of mortality from tuberculosis. The virus of tuberculosis creeps in most insidiously, all unnoticed, being in this respect analogous only to the virus of leprosy, of syphilis, or possibly of malaria in tropical countries. A eugonic bacillus is one which grows readily, a dysgonic bacillus one which grows with difficulty on artificial media.