Some missing measurements in comparative medicine.

At the present time it is difficult to make comparisons of animal diseases in various geographic areas. Some missing measurements which limit these comparisons are: the lack of an internationally accepted system to classify diseases; the lack of routinely collected information about animal births, diseases, and deaths; the lack of normal or standard values for many species; and the lack of methods to define animal populations at various points in time. Most of these problems have been faced and solved for human diseases. Work should be started immediately to develop similar research methods for animal diseases.