The experimental subject--a choice, not an echo.
D000820:Animal Diseases; D000818:Animals; D000830:Animals, Laboratory; D002415:Cats; D002685:Chiroptera; D004195:Disease Models, Animal; D004285:Dogs; D000882:Haplorhini; D008394:Marsupialia; D010684:Philosophy; D011998:Recreation; D012106:Research; D013552:Swine; D014730:Veterinary Medicine; D004490:Xenarthra