their respective spheres of activity, for we must assume that the crania of the Australians, having the small capacities just referred to, were yet sufficiently large for the lodgments of brains competent to perform the functions demanded by the life of a savage. From a large number of measurements of capacity which I have made of the skulls of the principal races of men, I would draw the following conclusions:- (1) That the average cranial capacity, and, consequently, the volume and weight of the brain, are marked higher in the civilized European than in the savage races; (2) that the range of variation is greater in the former than in the latter; (3) that in uncivilized man the proportion of male crania having a capacity equal to the European mean, 1,500 c.c., is extremely small; (4) that though the capacity of the men's skulls is greater than that of the women's, there is not quite the same amount of difference between the sexes in a savage as in a civilized race.

It may now be of interest to say a few words on the capacity of the cranium in the large anthropoid apes. I have measured, by the method already referred to, the capacity of the skulls of five adult male gorillas, and obtained a mean of 404 c. c., the maximum being 590 c. c., and the minimum 410 c. c., the range of variation being 180 c. c. Dr. Delisle found the old male orang (Maurice), which died a short time ago in the Jardin des Plantes, to have a capacity of 385 c. c., whilst the younger male (Max) had a capacity of 470 c. c. The mean of eleven specimens measured by him was 408 c. c., which is somewhat less than the measurements of males recorded by M. Topinard and Dr. Vogt, but it should be stated that in some of Dr. Delisle's specimens the sex could not be properly discriminated, and possibly some of them may have been females. The cranial capacity of seven male chimpanzees is stated by M. Topinard to be 421 c. c.

The determination of the mass and weight of the brain as expressed in ounces, and of the capacity of the cranial cavity as expressed in cubic centimetres, are only rough methods of comparing brain with brain, either as between different races of men or as between men and other mammals. Much finer methods are needed in order to obtain a more exact comparison.

as Size

Quality as well The school of phrenologists represented in the first half of the century by Gall, Spurzheim, and George Combe, whilst recognizing the importance of the size of the brain as a measure of intellectual activity, also attached value to what was called its quality. At that time the inner mechanism of the brain was almost unknown, for the methods had not been discovered by which its minute structure could be determined. It is true that a difference was acknowledged between the cortical grey matter situated on the surface of the hemispheres and the subjacent white matter. Spurzheim had also succeeded. in determining the presence of fibres in the white matter of the encephalon, and had, to a slight extent, traced their path. The difference between the smooth surface of the hemispheres of the lower mammals and the convoluted surface of the brain of man and the higher mammals and the influence which the development of the convolutions exercised in increasing the area of the cortical grey matter were also known.

A most important step in advance was made when, through the investigations of Leuret and Gratiolet, it became clear that the convolutions of the cerebrum, in their mode of arrangement, were not uniform in the orders of mammals which possessed convoluted brains, but that different patterns existed in the orders examined. By his further researches, Gratiolet determined that in the anthropoid apes, notwithstanding their much smaller brains, the same general plan of arrangement existed as in man, though differences occurred in many of the details, and that the key to unlock the complex arrangements in man was to be obtained by the study of the simpler disposition in the apes. These researches

have enabled anatomists to localize the convolutions and the fissures which separate them from each other and to apply to them precise descriptive terms. These investigations were necessarily prelimi nary to the histological study of the convolutions and to experimental inquiry into their functions.

Nerve-Cells By the employment of the refined histological methods now in use, it has been shown that the grey matter in the cortex of the hemispheres and in other parts of the

brain is the seat of enormous numbers of nerve cells, and that those in the cortex, whilst possessing a characteristic pyramidal shape, present many variations in size.

Further, that these nerve-cells give origin to nerve axial fibres, through which areas in the cortex become connected directly or indirectly either with other areas in the same hemisphere, with parts of the brain and spinal cord situated below the cerebrum, with the muscular system or with the skin and other organs of

sense.

Every nerve-cell with the nerve axial fibre arising from and belonging to it, is now called a neurone, and both brain and spinal cord are built up of tens of thousands of such neurones. It may reasonably be assumed that the larger the brain the more numerous are the neurones which enter into its constitution. The greater the number of the neurones, and the more complete the connections which the several areas have with each other through their axial fibres, the more complex becomes the internal mechanism and the more perfect the structure of the organ. We may reasonably assume that this perfection of structure finds its highest manifestations in the brain of civilized

men.

The specialization in the relations and connections of the axial fibre processes of the neurones, at their termination in particular localities, obviously points to functional differences in the cortical and other areas to which these processes extend. It has now been experimentally demonstrated that the cortex of the cerebrum is not, as M. Flourens conceived, of the same physiological value throughout, but that particular functions are localized in different areas and convolutions. In speaking of localization of function in the cerebrum, one must not be understood as adopting the theory of Gall, that the mental faculties were definite in their number, that each had its seat in a particular region of the cortex, and that the locus of this region was marked on the surface of the skull and head by a more or less prominent "bump."

The foundation of a scientific basis for localization dates from 1870, when Fritsch and Hitzig announced that definite movements followed the application of electrical stimulation to different areas of the cortex in dogs. The indication thus

given was at once seized upon by David Ferrier, who explored not only the hemispheres of dogs, but those of monkeys and other vertebrates. By his researches, and those of many subsequent inquirers, of whom amongst our countrymen we may specially name Beevor, Horsley, and Schafer, it has now been established that, when the convolutions bounding and in close proximity to the fissure of Rolando are stimulated, motor reactions in the limbs, trunk, head, and face follow, which have a definite purposive character, corresponding with the volitional movements of the animal. The Rolandic region is therefore regarded as a part of the motor apparatus; it is called the motor area, and the function of exciting voluntary movements is localized in its cortical grey matter.

Basis for Localization

By the researches of the same and other inquirers, it has been determined that certain other convolutions are related to the different forms of sensibility, and are sensory or perceptive centres, localized for sight, hearing, taste, smell, and touch.

Most important observations on the paths of conduction of sensory impressions in the cortex of the convolutions were announced last year by Dr. Flechsig of Leipsic, so well known by his researches on the development of the tracts of nerve-fibres in the columns of the spinal cord, published several years ago. He discovered that the nervefibres in the cord did not become myelinated, i. e., attain their perfect structure, at a uniform period of time, so that some acquired their complete functional importance before others. He has now applied the same method of research to the study of the development of the human brain, and has shown that in it also there is a difference in the time of attaining perfect structural development of the nervetracts. Further, he has discovered that the nerve-fibres in the cerebrum become myelinated, subsequent to the fibres of the other divisions of the cerebro-spinal nervous axis. When a child is born very few of the fibres of its cerebrum are myelinated, and we have now an anatomical explanation of the reason why an infant has so inactive a brain and is so helpless a creature. It will, therefore, be of especial interest to determine whether in those animals which are active as

Flechsig names the great sensory centre which receives the impulses associated with touch, pain, temperature, muscular sense, etc., "horperfuhlsphare," the region of general-body sensation, or the "somaesthetic' area, as translated by Dr. Barker. The tracts conducting these impulses myelinate at successive periods after birth. They pass upwards from the inner and outer capsules and the optic thalamus as three systems.

The Rolandic area, therefore, is not exclusively a motor area, but is a centre associated also with the general sensibility of the body. The motor fibres in it are not myelinated until after the sensory paths have been developed. As the motor paths become structurally complete, they can be traced downwards as the great pyramidal tract from the pyramidal nervecells in this area, from which they arise into the spinal cord, where they come into close relation with the nerve-cells in the anterior horn of grey matter, from which the nerve axial fibres proceed that are distributed to the voluntary muscles.

Flechsig's observations agree with those of previous observers in placing the visual centre in the occipital lobe; the auditory centre in and near the superior temporal convolution; and the olefactory centre in the uncinate and hippocampal convolutions. Of the position of the taste centre he does not speak definitely, although he thinks it to be in proximity either to the centre of general sensation or to the olfactory centre.

tions are situated, not directly associated with the reception of sensory impressions, or as centres of motor activity, the function of which is to be otherwise accounted for. These convolutions lie intermediary to the sensory and motor centres. Flechsig has shown that in them myelination of the nerve-fibres does not take place until some weeks after birth, so that they are distinctly later in acquiring their structural perfection and functional activity. As the nerve-fibres become differentiated, they are seen to pass from the sense-centres into these intermediate convolutions, so as to connect adjacent centres and bring them into association with each other. Hence, he has called them the Association Centres, the function of which is to connect centres and convolutions otherwise disconnected.

We have now, therefore, direct anatomical evidence, based upon differences in their stages of development, that, in addition to the sensory and motor areas in the cortex of the human brain, a third division - the association centres-is to be distinguished.

If we compare the cerebrum in man and the apes, we find these convolutions which constitute the motor and sensory centres distinctly marked in both. An ape, like a man, can see, hear, taste, smell and touch; it also exhibits great muscular activity and variety of movement. It possesses, therefore, similar fundamental centres of sensation and motion which are situated in areas of the cortex, resembling in arrangement and relative position, though much smaller in size than the corresponding convolutions in the adult human brain. It is not unlikely, though the subject needs additional research, that the minute structure of these centres resembles that of man, though from the comparatively restricted area of grey matter in the ape, the neurones will necessarily be much fewer in number. In the cerebrum of a new-born infant, whilst the motor and sensory convolutions are distinct, the convolutions for the association areas, though present, are comparatively simple, and do not possess as many windings as are to be seen in the brain of a chimpanzee not more than three or four years old.

Again, if we compare the brain of the Bush woman, miscalled the Hottentot Venus, figured by Gratiolet and by Bis

choff, or the one studied by Mr. John Marshall, with that of the philosopher Gauss, figured by Rudolph Wagner, we also recognize the convolutions in which the motor and sensory areas are situated. In all these brains they have a comparative simplicity of form and arrangement which enables one readily to discriminate them. When we turn, however, to the association areas in the three tiers of convolutions in the frontal lobe, and in the parieto-occipital and occipito-temporal regions where the bridging or annectant convolutions are placed, we cannot fail to observe that in a highly-developed brain, like that of Gauss, the association convolutions have a complexity in arrangement and an extent of cortical surface much more marked than in the Bush woman, and to a still greater degree than in the ape. The naked eye anatomy of the brain therefore obviously points to the conclusion that these association areas are of great physiological importance.

Their Function The problem which has now to be solved is the determination of their function. Prolonged investigation into the development and comparative histology of the brain will be necessary before we can reach a sound anatomical basis on which to found satisfactory conclusions. It will especially be necessary to study the successive periods of development of the nerve-fibre tracts in the cerebrum of apes and other mammals as well as the magnitude and intimate structure of the association areas in relation to that of the motor and sensory areas in the same species.

Flechsig, however, has not hesitated to ascribe to the association centres functions of the highest order. He believes them to be parts of the cerebral cortex engaged in the manifestations of the higher intelligence, such as memory, judgment and reflection; but in the present state of our knowledge such conclusions are, of course, quite speculative.

It is not unlikely, however, that the impulses which are conveyed by the intermediate nerve-tracts, either on the one hand from the sense centres to the association centres on the other, or from the association centres to the sensory and motor centres, are neither motor nor sensory impulses, but a form of nerve energy determined by the terminal connections and contracts of the nerve fibres.

It is possible that the association centres, with the intermediate connecting tracts, may serve to harmonize and control the centres for the reception of sensory impressions that we translate into consciousness with those which excite motor activity, so as to give to the brain a completeness and perfection of structural mechanism which, without them, it could not have possessed.

We know that an animal is guided by its instincts, through which it provides for its individual wants and fulfills its place in nature. In man, on the other hand, the instinctive acts are under the influence of the reason and intelligence, and it is possible that the association centres, with the intermediate association fibres which connect them with the sensory and motor centres, may be the mechanism through which man is enabled to control his animal instincts, so far as they are dependent on sensation.

The higher we ascend in the scale of humanity the more perfect does this control become, and the more do the instincts, emotions, passions, and appetites become subordinated to the self-conscious principle which regulates our judgments and beliefs. It will, therefore, now be a matter for scientific inquiry to determine, as far as the anatomical conditions will permit, the proportion which the association centres bear to the other centres both in mammals and in man, the period of development of the association fibres in comparison with that of the motor and sensory fibres in different animals, and, if possible, to obtain a comparison in these respects between the brains of savages and those of men of intelligence.

The capability of erecting the trunk; the power of extending and fixing the hip and knee joints when standing; the stability of the foot; the range and variety of movement of the joints of the upper limb; the balancing of the head on the summit of the spine; the mass and weight of the brain, and the perfection of its internal mechanism, are distinctly human characters. They are the factors concerned in adapting the body of man, under the guidance of reason, intelligence, the sense of responsibility and power of self-control, for the discharge of varied and important duties in relation to himself, his Maker, his fellows, the animal world, and the earth on which he lives.

F the many silent revolutions which electricity is effecting or is destined to effect in the immediate future, not the least, says a writer in the new publication, "Literature," is the complete transmogrification of that ugly necessity of modern industrialism, the factory. To-day most factories are a chaos of whirling belts and wheels. Tomorrow, if the electricians have their way, the buildings will be light and airy in structure and light and airy inside, and noiseless, compact, and economical electric motors will have replaced wasteful engines, shafting, and belting. So far, progress in this direction has been slow, and it is to increase the rate of advance that the author of the volume1 under review has written, in somewhat slap-dash style, his apology for the electric motor. In it he has summarized the encouraging results attained up to the present and has pointed out to the enterprising factoryowner the way in which he must go in future. In regard to the adoption of electrical working in factories, England, adds the reviewer, does not lag behind the rest of the world, and it is to be devoutly hoped that Mr. Scott's well-reasoned, well-written advocacy will, at least, have the effect of inciting the chiefs of industry to maintain the small lead we at present possess. Electric working means lower cost of production and safer and more healthy workshops.

From title-page to index this unpretentious little text-book2 is much to be commended. The author, unlike many we know, has selected a title which tells the potential purchaser of the book its exact scope; any one requiring to learn all about the practical design and construction of alternate-current machinery is warned off. On the other hand, students wishing to clear away misconceptions engendered in the lecture-room or engineers anxious to obtain a key to the many mysteries of alternate-current working, will

(1) The Local Distribution of Electric Power in Workshops. By Ernest Kilburn Scott, A. I. E. E. 137 pages. London, 1897. (Biggs. 2/-)

(2) The Principles of Alternate-Current Working. By Alfred Hay, B. Sc., Edin., Lecturer on Electrotechnics at the University College, Liverpool. 276 pages. London, 1897. (Biggs. 5/-)

find exactly what they want, lucidly set forth and without any parade of unnecessary mathematics, in the small compass of Mr. Hay's pages. There are in existence several more elaborate treatises on alternate-currents, but we are strongly inclined to the belief that, in Mr. Hay's book all the law and the prophets of alternate-currents is to be found. Of course, if a man propose to set up as a professor, he must master more than is therein contained, and, again, if he be a mathematical Hercules, he will find in alternate-current phenomena more than enough for twelve times twelve labors. But for the simple student or plain practical man a thorough mastery of Principles of Alternate-Current Working" should suffice, so far as mere booklearning is concerned; at any rate, it will prove a useful prelude to the mastery of portentous tomes, such as Dr. Fleming's well-known work on "The AlternateCurrent Transformer."

The

Hitherto, most writers on this subject would appear to have had a twofold object in view. Co-equal with their desire to make smooth the path of the student of alternate-currents has been their anxiety to air their mathematical skill. Mr. Hay, however, studiously avoids this capital error, and even the modicum of trigonometrical and vectorial mathematics, which he is compelled by the nature of his subject to make use of, is, itself, explained in his lucid and interesting introductory chapters. In the same easy style he explains the fundamental principles and puzzles of alternate-currents. The reader must be of abnormal mental density who does not rise from a perusal of these pages with his mind at rest as regards "root-mean-square values," "power factors," "form factors," "displacement currents," and such like dark and forbidding things.

Each chapter is followed by up-to-date references to the history and bibliography of the subject and by useful exercises calculated to test the knowledge acquired. Were it not for the exceeding roughness of the diagrams and the numerous misprints, for both of which defects the publisher and not the author is, no doubt, to blame, we should have nothing but good to speak of "The Principles of AlternateCurrent Working."