CORRESPONDENCE BETWEEN FORMS AND HABITS OF ANIMALS.
The most simple observation renders at once apparent a correspondence between the external form of animals, the general direction of their tendencies, and their habits.
Let us examine this question at somewhat greater length. From the age of Aristotle to the present time, zoologists have arranged the almost countless tribes of animals into a number of groups or divisions, more or less related in general habits and structure. All the classifications which have been hitherto proposed may be referred to one or the other of two general principles. Either the colour of the blood (Aristotle), the conformation of the heart (Hunter), the arrangement of the nervous system (Owen), or some other peculiarity of internal structure, has been selected as the basis of arrangement; or the animal creation has been grouped according to certain definite circumstances connected with outward form and configuration. As regards their internal organisation, the variations in the structure and arrangement of the nervous system affords by far the best means of classifying animals, and the whole animal world has accordingly been divided into five primary divisions. We have already endeavoured to prove that the manifestations of mind are only made known to us through the medium of corporeal organs, whatever may be the nature of its essence. By the state of the nervous system volition is modified or controlled, the operation of the senses accelerated or retarded, the muscular movements rendered feeble and uncertain, or strong, vigorous, and energetic; in fine, the chief manifestations of life, thought, volition, and independent motion, are all regulated by the condition and structure of the central nervine masses.