The difficulty of this view is that even with the high measure of care which the conditions of civilization permit us to devote to the effort, it has been found impossible to educate captive wolves to the point where they show any affection for their masters, or are in the least degree useful in the arts of the household or the occupations of the chase. They are, in fact, indomitably fierce and utterly self-regarding. It seems unreasonable to believe that any savage would have found either pleasure or profit from an effort to tame any of the known species of wolves. Moreover, the fact that dogs show little or no tendency to revert to the form and habits of their brutal kindred, or to interbreed with them, is clearly against the supposition that there is any close relation between the creatures. [Illustration: Greyhound after "the Kill"] Yet other speculative inquirers have sought the origin of the dog through the admixture of the blood of several different species, the wolf and the jackal being, perhaps, the principal or the only components of the hybrid stock. Here, too, the evidence of nature is against the supposition. No one has ever succeeded in hybridizing the wolf and the jackal, nor do our dogs show any more tendency to revert to the jackal than to the wolf. They meet their tropical relative with as much animosity as is proper, or at least customary, in the intercourse of allied yet distinct species. In fact, all the indices by which we are able to carry back the history of other domesticated animals to their primitive or even extinct ancestry, fail in the case of the dog. When the stock is allowed to go as nearly wild as they can be induced to become, we do not find that they thereby approach to any known wild form. It therefore seems reasonable to betake ourselves to another basis for the natural history of the dog, which has not yet been made a matter of much inquiry, but which promises to afford us more substantial truth than the conjectures which we have just considered.