The most popular small game mammal in nearly every part of North America is one or another of the species of rabbits or hares. The rabbit is one of the few species of wild game that still is hunted commercially and sold for food on the open market. The close association and repeated contact of man with these animals has resulted in his contracting such of their diseases as are transmissible to him.

Consequently the rabbits and hares have figured in many investigations concerned with public health and medicine. Because the number of such investigations is increasing, there has been an increasing number of specimens of these animals submitted to mammalogists for identification; also, inquiries are received as to the degree of relationship between two or more of the named kinds of rabbits in which identical, or closely related, disease organisms have been found; other inquiries have to do with the degree of relationship of named kinds of rabbits and hares in widely separated parts of the continent.