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THE POPULAR SCIENCE MONTHLY. 



has given, unquestionably, the clearest and 

 most interesting brief account yet made of 

 the structure and operations of the brain. 

 The books of Drs. Luys and Bastian are to 

 a great degree supplementary to each other. 

 Dr. Luys, in treating " The Brain and its 

 Functions," confines himself to the human 

 brain, and makes his work an exclusively 

 human study. Dr. Bastian, in his " Brain 

 as an Organ of Mind," deals comprehensively 

 with the supreme nerve-centers of the whole 

 animal series. His work is profusely illus- 

 trated with diagrams of the figure and an- 

 atomical structure of the brains of all grades 

 of animals ; while Dr. Luys, passing by the 

 whole scheme of inferior life, has but six 

 illustrations in his book, and these are de- 

 signed simply to make clear the offices and 

 relations of fundamental parts, so as to ex. 

 plain the corporeal conditions of psychical 

 processes. 



We have been fascinated by this volume 

 more than by any other treatise we have 

 yet seen on the machinery of sensibility 

 and thought ; and we have been instructed 

 not only by much that is new, but by many 

 sagacious practical hints such as it is well 

 for everybody to understand. Lest we be 

 thought to speak too strongly in commenda- 

 tion of the sterling character of this work, 

 and in order to give some idea of the au- 

 thor's method, we quote the following excel- 

 lent statement concerning it from the col- 

 umns of the " St. James Gazette " : 



No living physiologist is better entitled to 

 speak with authority upon the structure and 

 functions of the braiu than Dr. Luys. His 

 studies on the anaiomy of the nervous system 

 are acknowledged to be the fullest and most 

 systematic ever undertaken. He begins by 

 treating the soft and delicate material of the 

 brain-tissues with chromic acid, which hardens 

 it so as to fix it sufficiently for the purposes of 

 laboratory work, without altering or distorting 

 its essential constitution. He then cuts off very 

 thin slices of the tissue one after another, and, 

 by employing different chemical reagents for 

 which the various minute elements of the brain 

 have varying susceptibilities, he obtains trans- 

 parent colored sections of the nervous matter, 

 which throw into strong relief the distinction 

 between cells and fibers, besides exhibiting 

 clearly the nature and direction of their intri- 

 cate ramifications. In this manner he has sys 

 tcmatically made many thousand delicate sec- 

 tions of brains, horizontally, vertically, and 

 laterally, at distances of a millimetre from one 

 another, each of which he photographs, till at 



. last he has succeeded in producing a series of 

 I maps of its entire structure which place the 

 relations of its organs in strikingly novel lights. 

 The first division of his present volume is de- 

 voted to summing up briefly the main results of 

 these important researches. The late Professor 

 Clifford has already popularized them in part 

 for the English reader ; but we believe this is 

 the first time that they have been definitely set 

 forth in any fullness before the general public 

 on this side of the Channel. 



Confining his attention to the cerebral hemi- 

 spheres alone, without entering into any par- 

 ticulars as to the cerebellum and other minor 

 appendages, Dr. Luys begins by pointing out 

 the fundamental distinction between the nerve- 

 cell or real central organ and the nerve-fiber or 

 connecting thread. The first answers to the 

 telegraph-office, the second to the wire uniting 

 one office with another. The gray matter which 

 forms the outer covering of the convolutions 

 consists of closely packed cells, and is thus 

 really the essentia] brain ; the white matter in 

 the center consists of fibers aggregated into 

 bundles, and is thus really a mass of large nerves. 

 Of thfc single cells themselves, with their nu- 

 merous converging fibers, as well as of their 

 arrangement in superimposed layers, Dr. Luys 

 gives very graphic and instructive diagrams. 

 The business of the cells individually and of Ihe 

 gray matter as a whole is to receive sensory 

 messages from the external organs of the senses 

 and to transform or to co-ordinate their im- 

 pulses into the proper movements as, for ex- 

 ample, when we see a fruit orflower, and stretch 

 out our hands to pick it. The white substance 

 is shown to consist of numerous interlacing 

 fibers, having for their function the conveyance 

 of such information from without inward, or 

 the carrying down of such motor impulses from 

 within outward. Their definite arrangement in 

 regular lines between the two hemispheres, as 

 well as between the surface of the convolutions 

 and the optic thalami and corpus striatum, is 

 admirably shown by diagrammatic figures. This 

 is the most important result of all Dr. Luys's 

 work. He has made it clear that sense-impres- 

 sions traveling from the eyes, ears, or skin, 

 arrive first at the bodies known as the optic 

 thalami ; that they are there re-enforced and 

 worked up, as it were, in special ganglia ; and 

 that they are thence reflected to the surface of 

 the hemispheres, where they are finally con- 

 verted into appropriate movements. He has 

 also fairly settled the fact that certain minor 

 bodies within the optic thalami are closely con- 

 nected with the main nerves of sight, smell, 

 taste, and hearing respectively, and that they 

 must be considered as subordinate or inter- 

 mediate centers where the data supplied by 

 those senses are put into shape for considera- 

 tion on the surface of the brain. The normal 

 course of an excitation in the sense-organs 

 seems to be this : it first proceeds along the 

 fibers to its own subordinate center in the 

 thalami ; it then passes up to the correspond- 

 ing portion of the convolutions ; it there for the 



