Relevance of animal studies to human disease

Increasing restrictions on the experimental use of human subjects and the difficulties of either evaluating or controlling human subjects over long periods of time suggest the need for increasing use of experimental animals, especially in the study of chronic disease. Experience appears to provide the only guideline for the selection of the most useful species in any particular field. It should be recognized that the species that are most susceptible or those that most nearly approximate the lesion found in man are not necessarily the only useful species. Differences in susceptibility or metabolism provide opportunities for identifying significant parameters in man. We tend to be locked into the use of a few experimental species for no obvious logical reason and have not yet begun to utilize the potential of the diverse species available. Whatever the experiment, diet remains an environmental variable that should be considered in the design and evaluation.