The distinction does not seem to lie principally in the range and delicacy of direct sensation, as may be judged from such well-known facts as man s inferiority to the eagle in sight, or to the dog in scent. At the same time, it seems that the human sensory organs may have in various respects acuteness beyond those of other creatures. But, beyond a doubt, man possesses, and in some way possesses by -virtue of his superior brain, a power of co ordinating the impressions of his senses, which enables him to understand the world he lives in, and by understanding to use, resist, and even in a measure rule it. No human art shows the nature of this human attribute more clearly than does language. Man shares with the mammalia and birds the direct expression of the feelings by emotional tones and inter] ectional cries ; the parrot s power of articiilate utter ance almost equals his own; and, by association of ideas in some measure, some of the lower animals have even learnt to recognise words he utters. But, to use words in them selves unmeaning, as symbols by which to conduct and convey the complex intellectual processes in which mental conceptions are suggested, compared, combined, and even analysed, and new ones created this is a faculty which is scarcely to be traced in any lower animal. The view that this, with other mental processes, is a function of the brain, is remarkably corroborated by modern investigation of the disease of aphasia, where the power of thinking remains, but the power is lost of recalling the word corresponding to the thought, and this mental defect is found to accompany a diseased state of a particular locality of the brain (see Aphasia). This may stand among the most perfect of the many evidences that, in Professor Bain s words, " the brain is the principal, though not the sole organ of mind." As the brains of vertebrate animals form an ascending scale, more and more approaching man s in their arrangement, the fact here finds its explanation, that lower animals perform mental processes corresponding in their nature to our own, though of generally less power and complexity. The full evidence of this correspondence will be found in such works as Brehm s Thierleben ; and some of the salient points are set forth by Mr Darwin, in the chapter on " Mental Powers," in his Descent of Man. Such are the similar effects of terror on man and the lower animals, causing the muscles to tremble, the heart to palpitate, the sphincters to be relaxed, and the hair to stand on end. The phenomena of memory, both as to persons and places, is strong in animals, as is manifest by their recognition of their masters, and their returning at once to habits disused for many years, but of which their brain has not lost the stored-up impressions. Such facts as that dogs " hunt in dreams," make it likely that their minds are not only sensible to actual events, present and past, but can, like our minds, combine revived sensa tions into ideal scenes in which they are actors, that is to say, they have the faculty of imagination. As for the reasoning powers in animals, the accounts of monkeys learning by experience to break eggs carefully, and pick off bits of shell, so as not to lose the contents, or of the way in which rats or martens after a while can no longer be caught by the same kind of trap, with innumerable similar facts, show in the plainest way that the reason of animals goes so far as to form by new experience a new hypothesis of cause and effect which ill henceforth guide their actions. The employment of mechanical instruments, of which instances of monkeys using sticks and stones, and some other similar cases, furnish the only rudimentary traces among the lower animals, is one of the often quoted distinctive powers of man. With this comes the whole vast and ever-widening range of inventive and adaptive art, where the uniform hereditary instinct of the cell- forming bee and the nest-building bird are supplanted by multiform processes and constructions, often at first rucl3 and clumsy in comparison to those of the lower instinct, but carried on by the faculty of improvement and new invention into ever higher stages. " From the moment, writes Mr Wallace (Natural Selection, p. 325), " when the first skin was used as a covering, when the first rude spear was formed to assist in the chase, when fire was first used to cook his food, when the first seed was sown or shoot planted, a grand revolution was effected in nature, a revolution which in all the previous ages of the earth s history had had no parallel; for a being had arisen who was no longer necessarily subject to change with the changing universe, a being who was in some degree superior to nature, inasmuch as he knew how to control and regulate her action, and could keep himself in harmony with her, not by a change in body, but by an advance of mind."
As to the lower instincts tending directly to self-preserva tion, it is acknowledged on all hands that man has them in a less developed state than other animals ; in fact, the natural defencelessness of the human being, and the long- continued care and teaching of the young by the elders, are among the commonest themes of moral discourse. Parental tenderness and care for the young are strongly marked among the lower animals, though so inferior in scopo and duration to the human qualities ; and the same may be said of the mutual forbearance and defence which bind together in a rudimentary social bond the families and herds of animals. Philosophy seeking knowledge for its own sake ; morality, manifested in the sense of truth, right, and virtue; and religion, the belief in and communion with superhuman powers ruling and pervading the universe, are human characters, of which it is instructive to trace, if possible, the earliest symptoms in the lower animals, but which can there show at most only faint and rudimentary signs of their wondrous development in mankind. That the tracing of physical and even intellectual continuity between the lower animals and our own race, does not necessarily lead the anthropologist to lower the rank of man in the scale of nature, cannot be better shown than by citing one of the authors of the development theory, Mr A. R. Wallace (op. cit., p. 324). Man, he considers, is to be placed " apart, as not only the head and culminating point of the grand series of organic nature, but as in some degree a new and distinct order of being."
To regard the intellectual functions of the brain and nervous system as alone to be considered in the psychological comparison of man with the lower animals, is a view satisfactory to those thinkers who hold materialistic views. According to this school, man is a machine, no doubt the most complex and wonderfully adapted of all known machines, but still neither more nor less than an instrument whose energy is provided by force from without, and which, when set in action, performs the various operations for which its structure fits it, namely, to live, move, feel, and think. This doctrine, which may be followed up from Descartes s theory of animal life into the systems of modern writers of the school of Moleschott and Biichner, underlies the Lectures on Man of Professor Carl Vogt, one of the ablest of modern anthropologists (English translation published by Anthropological Society, London, 1864). Such views, however, always have been and are strongly opposed by those who accept on theological grounds a spiritualistic doctrine, or what is, perhaps, more usual, a theory which combines spiritualism and materialism in the doctrine of a composite nature in man, animal as to the body and in some measure as to the mind, spiritual as to the soul It may be useful, as an illustration of one opinion on this subject, to continue here from an earlier page the citation of Dr Prichard s comparison between man and the lower animals:—
