Later investigations made by Park and Krumweide, of the Research Laboratory of New York City, Novick, Richard M. Smith, Ravenel, Rosenau, Chung Yik Wang, and others tend to show the incidence of bovine infection in the human family. Chung Yik Wang stated in 1917 that studies of 281 cases of various clinical forms of tuberculosis in Edinburgh, Scotland, resulted in the isolation of the bovine tubercle bacilli in 78.4 per cent of cases under the age of 5 years, in 70.3 per cent between the ages of 5 and 16, and in 7.8 per cent over the age of 16. This investigator states that from the prophylactic point of view any measure resorted to in combating the disease should be directed not only against the human spread of infection, but also, more particularly in children's cases, against the bovine source of infection.
Ravenel, in summarizing the work of Drs. Park and Krumweide, as well as others throughout the world, gives the following results:
Of 63 children dying of tuberculosis at the babies' hospital 59 cases proved to be human infection and 4 bovine, a percentage of 6-1/3.
Of 9 children dying of tuberculosis at the foundling hospital 4 proved to have derived their infection from human sources and 5 from bovine, a percentage of 55.
Of a total of 88 children under 5 years of age who died of tuberculosis 77 proved to have derived their infection from human sources and 11 from bovine, a percentage of 12½.
Combining the cases studied in New York with those of other observers in different parts of this country and Europe, the following results are obtained:
Adults, 787 cases—777 human and 10 bovine infection.
Children, 5 to 16 years, 153 cases—117 human and 36 bovine infection.
Children under 5 years, 280 cases—215 human and 65 bovine infection.