Dr. Kane tells us that one of the Newfoundland dogs which spent two arctic winters with him was so oppressed by the darkness and solitude of the long night, and so reduced in strength by hardship and cold, that it at last became insane, and manifested all the symptoms which were observed in some of the human beings of the party who were affected in the same way by the same causes.
Many animals, poultry for instance, have special cries for special purposes: an alarm-cry to indicate danger; a call to announce the discovery of a supply of food; a maternal "cluck" to keep the brood of chicks together; and several other cries, each of which has a meaning. These cries are undoubtedly produced and understood by the fowls instinctively, but the process by which man learns to recognize them and to understand their meaning is purely intellectual. The farmer's dog learns to distinguish and understand them as well as the farmer himself, and knows when he may be unconcerned, and when he is to go to their defense; and there is not the slightest reason to doubt that he acquires his knowledge, as man does, by a process of observation, memory, and thought. Instances of intelligence among the higher mammalia could, of course, be indefinitely multiplied, but it does not seem necessary to dwell upon the subject here. I will, however, give a few examples of what seems to be intelligence among the lower animals. I think it was Lubbock who observed a spider which wished to raise a captured wasp to a more elevated portion of the web. Finding it too heavy, it stopped its efforts and gnawed off two of the wings, and then made a second attempt. As it was still too heavy, it lightened it still further, and again tested it, and repeated the process until it had reduced its load to a manageable size. I am unable to give the authority for the following, but think the account was published in Nature some years since: A gentleman found a small dead bird and impaled it upon a stick, and stuck the other end of the stick into the ground near some "scavenger" beetles. The instinct which leads these insects to bury dead birds and other animals as a provision for the wants of their young is well known. In this case they soon found the bird—but how was a bird perched upon an upright stick to be buried in the ground? After some consultation they resorted to the very clever expedient of digging up the stick, and then digging a hole large enough to bury both bird and stick. Although this seems very like intelligence, it may possibly be explained as a case in which the ordinary instinctive habit of the animal accidentally fitted an exceptional demand upon it.
Many of the actions of ants, however, do not admit of any such interpretation. When two armies of ants of different species leave their homes at the same time, arrange themselves in ranks, and march to a point of meeting, and engage in battle, they exhibit, not simply proofs of concerted action, but evidences that they can arrange and plan to meet extraordinary and unusual emergencies.