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Rh among animals for the purpose of reaching a better understanding of those which are committed by men? If animals are liable to the greater proportion of the organic maladies to which we are subject, if they are liable to epidemic or contagious diseases, there appears to be no reason why they should be exempt from mental diseases. Just as we recognize that there occur among men malformed individuals, organically defective and furnishing proofs of their organic faults in their acts, feelings, or thoughts, so we should expect to find similar individuals among animals, or at least among those species which stand constitutionally nearer to man.

Two causes may be alleged for the neglect of this study: First, animal psychology has not yet made much progress. The investigations of veterinary physicians have not been directed to that side. Pierquin said, in his "Traité de la Folie des Animaux" (Treatise on Madness among Animals), in 1839, that till his time no professor of veterinary medicine had ever spoken from his chair, either of the brain, the nervous system, or the physiology of animals. The other cause, and the most influential one, has been the difficulty most authors have had in disembarrassing themselves of the scholastic ideas which have promoted the belief in a great chasm between the moral condition of animals and of men. As Gall has well said, the greatest obstacle that it has ever been possible to oppose to the knowledge of human nature consists in the fact that theorists have isolated it from that of other beings, and endeavored to subject it to laws of its own, different from those of their nature. He adds, subsequently: "Those who account for the normal and intellectual acts of man, of the understanding and of the will, independently of the body, and those who, being wholly strangers to the natural sciences, still believe in the mechanism or the automatism of brutes, may find the comparison of man with animals revolting and absolutely sterile. But such a comparison will be regarded as indispensable by those who have familiarized themselves with the labors of Bonnet, Condillac, Reimarus, Georges Leroy, Dupont, Nemours, Herder, Cadet Devan, Huber, etc., and especially by those who have become ever so slightly acquainted with the progress of comparative anatomy and physiology."

The authors who are cited by Gall have furnished important data for the comparison of animal species, and have laid the foundation of a scientific comparative physiology. Buff on had already asserted that, if no animals existed, the nature of man would be still more incomprehensible than it is. The observations of Georges Leroy and Gall have shown that the elementary functions of the brain must be investigated in the study of animals. These authors have been followed in this way by Prichard, Pierquin, Darwin, Forel, Espinas, Houzeau, Büchner, etc., from whom and from other naturalists and travelers, the materials for this essay have been largely borrowed.

The present work was suggested to me by Professor Lambrozzo, of