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Rh and higher-lying grey portions of the nervous centres there is an a priori presumption in favour of the extension of this principle of localization. This has been premised on metaphysical as well as on anatomical grounds. A. B. Bonnet long ago believed each portion of the brain to have a specifically separate function, and Herbert Spencer has said that “no physiologist can long resist the conviction that different parts of the cerebrum subserve different kinds of mental action. Localization of function is the law of all organization; separateness of duty is universally accompanied with separateness of structure, and it would be marvellous were an exception to exist in the cerebral hemispheres. Let it be granted that the cerebral hemispheres are the seats of the higher psychical activities; let it be granted that among these higher psychical activities there are distinctions of kind which, though not definite, are yet practically recognizable, and it cannot be denied, without going in direct opposition to established physiological principles, that these more or less distinct kinds of psychical activity must be carried on in more or less distinct parts of the cerebral hemisphere.”

For a masterly review of the old and the new association and localization theories, see W. Wundt's Grundzüge der physiologischen Psychologie, i. 289 sqq.; also the same author's Essays, Leipzig (1888), pp. 109 sqq.

There is a large weight of evidence in favour of the existence of some form of localization of function. So little is known of the physical changes which underlie psychical phenomena, or indeed of the succession of the psychical processes themselves, that we cannot as yet judge as to the nature of the mechanism of these centres. So much of the psychic work of the individual life consists in the interpretation of sensations and the translation of these into motions that there are strong a priori grounds for expecting to find that much of the material of the nerve-centres is occupied with this kind of work, but in the present conflict of experimental evidence it is safer to suspend judgment. That these local areas are not centres in the sense of being indispensable parts of their respective motor apparatuses is clear, as the function abolished by ablation of a part returns, though tardily, so that whatever superintendence the removed region exercised apparently becomes assumed by another part of the brain. Experimental physiology and pathology, by suggesting other functions for parts of the brain-surface, are thus directly subversive of many details of the phrenology of Gall and Spurzheim.

Psychological Aspect.—The fundamental hypothesis which underlies phrenology as a system of mental science is that mental phenomena are resolvable into the manifestations of a group of separate faculties. A faculty is defined as “a convenient expression for the particular states into which the mind enters when influenced by particular organs; it is applied to the feelings as well as to the intellect, thus the faculty of benevolence means every mode of benevolence induced by the organ of benevolence” (Combe). In another work the same author says it is “used to denote a particular power of feeling, thinking, perceiving, connected with a particular part of the brain.” The assumption is contained in the definition that the exercise of a faculty is the physical outcome of the activity of the organ, and in several of the standard works this is illustrated by misleading analogies between these and other organs; thus the organs of benevolence and of firmness are said to be as distinct as the liver and pancreas. The mind, according to another author, consists of the sum of all the faculties. In this view the unity of consciousness is somewhat difficult to explain, and consequently there is assumed by others a single unifying substratum, and on this the organs are supposed to act; thus thoughts are defined as “relations of the simple substance, mind, to certain portions of the encephalon” (Welsh, Phren. Journ. i. 206). Gall himself believed that there was but a single principle which saw, felt, tasted, heard, touched, thought and willed (Fonctions du cerveau, i. 243); and the American exponent of phrenology, Caldwell, says “the mind is as single in its power as it is in its substance;

it is a quickening and operating principle, essential to all the mental faculties, but does not, by any means, possess them itself” (Elements, p. 16). It is not easy to understand the supposed relation of this hypothetical substratum to the separate faculties acting on it. It must be both immaterial and unconnected with the brain, as the whole two thousand million cells supposed to exist in the cerebral hemispheres are all parcelled out among the faculties, and none are left for the unifying nous.

Each organ is considered as engaged, either independently in bringing forth its own product, or collectively with others in elaborating compound mental states, and according to their several degrees of development and activity they are considered capable of perceiving, conceiving, recollecting, judging or imagining each its own subject. This mechanical conception of the division of labour in the production of the phenomena of mind has the charm of simplicity, but is attended with the difficulty that arises in discriminating the operations of the different organs one from the other. Phrenologists are apt to be vague respecting the limits of the several faculties, as about the boundaries of the separate organs. It was pointed out by Jeffrey that the lines of demarcation between benevolence, adhesiveness and philoprogenitiveness were indeterminate, although the organs are not very close, and the same applies to other organs.

It is unfortunate for the clearness of the definition that, although historically the faculties were the first phenomena noted, independent of and previous to their localization, yet in the definition the faculties are defined in terms of their localities.

The following arguments are adduced in favour of the fundamental separateness of the faculties: (1) analogy—elsewhere in the animal economy division of labour is the rule; (2) the variety of mental endowment observed among children before they are influenced by education, and the inequalities in the mental endowments of individuals; (3) the phenomena of insanity, especially of monomania; (4) the varying periods at which individual faculties attain their maximum development; (5) the phenomena of dreams, and the awakening of a limited number of faculties during them; (6) pain being felt in an organ when it is overtaxed.

Such faculties are supposed to be primary—(1) as exist in some animals and not in others, (2) as vary in their development in the sexes, (3) as are developed in varying proportions with regard to other faculties, (4) as may act separately from other faculties, (5) as are not necessarily simultaneous with other faculties in action, (6) as are hereditary, and (7) as may be singly diseased.

According to the development of their powers mankind may be divided into six classes: (1) those in whom the highest qualities are largely developed and the animal qualities feeble; (2) those with the reversed conditions developed, with large animal and feeble intellectual and moral faculties; (3) those in whom good and evil are in constant war, with active animal and strong intellectual faculties and sentiments; (4) those partial geniuses in whom a few qualities are unusually developed, while the rest are at or below the mediocre standard; (5) those men of moderate endowment in whom some faculties are nearly or quite deficient; (6) those with an unvarying standard of undistinguished mediocrity in all their faculties.

It is perhaps unfortunate that the word “faculty” has been used in this sense of original power by phrenologists. It would have been better to employ, as Mr Lewes suggests, the term