Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/883

PHRENOLOGY 847 7. The phrenological want of knowledge of the topography of the brain-surface was necessarily correlated with ignorance of the exact relations of the convolutions to the interior of the cranial bones ; these have been carefully worked out by Huschke, Heffler, Turner, and Reid. Some latitude, however, must be allowed in topography, as the exact relation of convolution to skull varies with the shape of the skull. Giacomini showed that the fissure of Rolando is perceptibly farther back from the coronal suture in dolichocephalic than in brachycephalic skulls, and it is still farther back in the extreme boat-shaped form of long-headedness. Passet shows that there is a slight topographical difference in the two sexes (Arch. f. Anthrop., 1882, xiv. 89), and in the heads of those with uiisymmetrically-shaped skulls there is often a want of lateral symmetry of convolution. Artificial deformations likewise alter the topographical relations of convolutions, and have served not a little to puzzle the phrenologist. Thus, the artificial dolichocephaly of the Caribs having bulged the squama occipitis, they decided that these people must be amiable lovers of children, 1 &c. 8. The existence of structural differences between different areas of cerebral surface is important to any theory of cerebral localiza tion, but no phrenologist has given us any original information on this point. Since the investigation of Baillarger, 2 it has been shown that some local differentiations of structure do really exist. Thus in the convolutions around the fissure of Rolando the gan glion-cells of the fourth layer are of large size (giant-cells of Betz), and in the convolutions of the temporo-sphenoidal lobe a layer of small angular cells (granule-cells) is interposed between the larger pyramidal and the ganglion-cells, so that, while in the parts of the brain above the fissure of Sylvius the grey cortex is for the most part five-layered, below and behind that fissure it is six-layered. There is no abrupt passage from the one to the other, the only sudden transition of structure of the grey cortex being at the hippocampal sulcus ; and giant-cells, although of smaller size, and less like those of the anterior cornu of the spinal cord, are scattered over other parts of the cerebral grey matter. 3 In fig. 71, vol. i. p. 874, the relations of the convolutions to the internal surface of the skull are represented, and their want of accurate correlation to the phreno logical areas can be seen by comparing that figure with the fore going series. The teachings of anatomy with regard to phrenology may be summarized thus : (1) the rate of growth of brain is concurrent with the rate of development of mental faculty ; (2) there is some degree of structural differentiation as there are varying rates of development of different parts of the cerebral surface ; (3) there is no accordance between the regions of Gall and Spurzheim and definite areas of cerebral surface. Physiological Aspect. The theory of some of the older metaphysicians, that the mind, in feeling and reflexion, makes use of no material instrument is not now accepted by psychologists. It was advanced by Brougham and Jeffrey as against the theory of phrenology ; but the doctrine that the brain is the organ of the mind is now universally received. While it is probable that certain molecular changes in the grey matter are antecedents or concomitants of mental phenomena, the precise nature of these processes, to what extent they take place, or how they vary among themselves have not as yet been deter mined experimentally ; the occurrence of the change can only be demonstrated by some such coarse method as the altered pulsation of the carotid arteries, 4 the increase of the temperature of the head, 5 the abstraction, during brain- action, of blood from other organs as shown by the plethys- mograph, or the formation of lecithin and other products of metabolism in brain -substance. As yet not a single step has been made towards the understanding of the con nexion between the molecular changes in the nerve-cell and the phenomena of thought and feeling. While our 1 Martius tells us that the Cavibs castrate their own children, fatten and eat them, an abuse of the organ of philoprogenitiveness ; see also Garcilaso de la Vega, Hist, des Incas, i. 12. 2 Mem. de I Acad. de Medecine, 1840, viii. 149. 3 For further particulars of structure, in addition to the authors quoted at vol. i. p. 878, see Bevan-Lewis and Clark, P. R. S., 1878, and Phil. Trans., 1880 and 1882. 4 See Eugene Gley, "Sur les Conditions Physiologiques de la Pensee," in Archives de Physiologic, 1881, 742. 5 Lombard, N. Y. Med. Journal, June, 1867, and Experimental Researches on the Regional Temperature of the Head, London, 1872. knowledge of the anatomy of the brain, especially of the grey nuclei and of the white bands uniting them, has within the last few years become much more accurate, brain-function has not as yet been so definitely determined ; indeed, much of nerve-physiology, especially that part which relates to the division of labour in the nerve-centres, is largely hypothetical and based on anatomical structure. Certain masses of grey nerve-matter situated in the spinal cord and medulla oblongata are so linked by nerve-cords to organs outside the nervous system which are set apart for the discharge of separate functions that they obviously form parts of the mechanism for the fulfilment of such functions. In the cases where these can be subjected to experiment we learn that they are nervous centres presid ing over the discharge of such functions ; and it has been determined by experiment, or else deduced from anatomical structure, that in those lower parts of the nervous centres which are more directly connected with the segmental elements of the body there is a certain localization of function ; hence the centres of pelvic actions, of respira tion, cardiac action, and inhibition of vaso-motor influence, deglutition, secretions, &c., can be mapped out in ascend ing series. As certain of these centres are united by bands of fibres to the larger 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. Bonnet 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 whatever ; separateness of duty is universally accompanied with separateness of struc ture, 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 the results of experiment on the brain, see PHYSIO LOGY, section " Nervous System." There is a large weight of evidence, which cannot be explained away, 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 them selves, 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 sen sations and the translation of these into motions that there are strong a priori grounds for expecting to find much of the material of the nerve-centres occupied with this kind of work, but in the present conflict of experimental evi dence 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. 6 Experimental physiology and pathology, by suggesting other functions for much of the brain-surface, are thus directly subversive of much of the phrenology of Gall and Spurzheim. 6 For cases, see Rochefontaine, Archives de Physiologic, 1883, 28 ; Bianchi, La Psichiatria, i. 97.