April 19, i88«] 



NATURE 



579 



nowadays admits that the evolution of mind and the evo- 

 lution of the nervous system proceeded pari passu, and 

 indeed are but two aspects of the same process." It is 

 hardly consistent with a further statement that this way 

 of regarding them is not only neglected but " derided and 

 scouted." Dr. Mercier asks for our sympathy for having 

 been for the last ten years as "the voice of one cry- 

 ing in the wilderness." Other voices, however, have 

 for long been heard there, if indeed that can be called a 

 wilderness which is peopled by the number who admit 

 the above-mentioned proposition in regard to the evolu- 

 tion of the mind and the nervous system. 



This work expounds Spencerian doctrines with much 

 fulness of diction, and in a style which is forcible, not to 

 say somewhat dogmatic. We find Spencer's illustration 

 of molecular movements from bricks on end reproduced, 

 and we may quote the following passage as a fair example 

 of the author's style : — 



" Imagine a brick set up on end. To do this requires the 

 expenditure of force. Now, if the ground is shaken the 

 brick falls, and liberates in falling a force equal to that 

 expended in raising it. Again, imagine a brick set on 

 end with another brick placed across the top of it. The 

 upper brick can now be knocked off the lower, and the 

 force which raised it be liberated, while the lower brick is 

 left standing, with the force that raised it still in store. It 

 is evident that a brick balanced on the top of another 

 one will be displaced by a gentler shake than is required 

 to knock down the single brick. . . . Now suppose more 

 and more bricks are added until we have quite a compli- 

 cated structure composed of loose bricks. It is easy to 

 see how readily a top brick could be knocked off. . . , 

 Now if we imagine these bricks to be connected to the 

 pile by elastic bases, so that when they have been 

 knocked down they will slowly rise again, with perhaps a 

 httle help, to their erect position, we shall have a diagram 

 which will represent very roughly what we suppose to be 

 the mechanism of the nervous discharge " (p. 23). 



Dr. Mercier's copious vocabulary clothes an idea in 

 many folds of attire. It is, we think, sometimes over- 

 loaded and too diffuse. Endowed with a large organ of 

 comparison, he illustrates his _theme with a redundant 

 variety of illustrations or makes one illustration do duty 

 in many forms. Great facility of expression enables him 

 to enforce his views, though it may be at the risk of pro- 

 ducing weariness by excessive iteration. He revels in 

 the description of molecules — their form, their relative 

 position, their polarity, their life, their behaviour, and 

 their destiny. M. Renan has been said to know more 

 about St. Paul than the apostle knew himself. Similarly 

 Dr. Mercier would, we are quite sure, be found to know 

 more about the molecules of the brain than, were they 

 gifted with consciousness, they would know themselves. 

 He might write a charming story entitled "The Bio- 

 graphy of a Cerebral Molecule," The author divides his 

 subject into three sections : Nervous Process, Conduct, 

 and Mind, the first underlying the other two. In treating 

 of " nervous discharge " he argues that the building up of 

 a molecule implies force ; this remains latent, stored up 

 in the gray matter. It is liberated at intervals— that is, 

 during functional activity. The rearrangement of atoms 

 in the molecule may be called " decompounding," while 

 the process of destruction is more properly termed 

 " decomposition." Thus, then, the former, together with 

 the liberation of force accompanying it, is the "dis- 



charge." It tends to spread. How is the Hberated force 

 replaced.^ Dr. Mercier cannot tell. All that can be 

 said is that it is a part of the general system of bodily 

 nutrition. Passing on to "nervous resistance," it is 

 assumed that there is a balance of tension and resistance 

 in the gray matter of the brain. The subject is worked 

 out ingeniously, and as fully as it admits of. Necessarily 

 much is altogether inferential. The hypothetical nature 

 of the doctrines taught by the Spencerian school no 

 doubt deters not a few from adopting them. Such 

 persons say that they are not scientifically proved, and 

 they challenge those who insist on their importance to 

 show that they can practically help the physician in his 

 treatment of mental affections. A homely simile illus- 

 trates the doctrine of continuous resistance. A charged 

 soda-water bottle resembles the tension of a charged 

 nerve-cell. Withdraw the cork, and the resistance of the 

 narrow neck causes an intermittent escape. The contents 

 " come blobbing out in a succession of intermittent 

 bursts," and so, according to the author, the narrow necks 

 of nerve-cells — the fibres which proceed from them - 

 cause analogous results. 



One chapter is devoted to the co-ordination and inhibi- 

 tion of muscular action. Nervous discharges are re- 

 garded in terms of the latter. The discharge of 

 an area of gray matter occasions normal movements. 

 The simultaneous beginning, duration, and ending of 

 muscular action depend upon the simultaneous issue 

 of a current of force to each muscle under its influ- 

 ence (p. 67). The nerves of muscles connnect them with 

 the cells of the gray matter of the brain, and muscular 

 force depends upon the amount of nerve-discharge. Co- 

 ordinated movements are secured by the group of nerve- 

 elements called a nerve-centre. The initiatory impulse 

 may come directly from the outside world — the environ- 

 ment. In some instances, however, this action is indirect 

 and distant, as, when reflection ends in acts set going 

 by "currents starting from the highest centres." To 

 terminate the action set up, another stimulus is necessary, 

 unless exhaustion itself terminates it. Here comes in the 

 element of control or inhibition to which all nerve-centres 

 are presumed to be subject, and by which they are re- 

 tained in a condition of mobile equilibrium as surely as 

 the planets in their orbits by the opposition of attraction 

 to their own inertia. It is forcibly argued that this influ- 

 ence is derived from centres having other functions, and 

 not from one exclusively set apart for this purpose. In- 

 hibition is, in short, a higher degree or power of the 

 resistance which causes the intermittent escape of nervous 

 force. A wide question is here raised, and there is not as 

 yet a consensus of opinion among physiologists in regard 

 to it. " Movements" are dealt with in much detail. The 

 section on the co-ordination of movements is an ela- 

 borate study of the subject. In the discussion of the 

 nervous mechanism of co-ordination and inhibition, occa- 

 sion is taken to give a minute description of Jacksonian 

 epilepsy. In inhibition the centres which supply the im- 

 pulse to start and accelerate, supply also the impulse which 

 arrests and retards. In walking, for instance, the centres 

 which actuate and regulate it are so arranged that they 

 control those below, they themselves being under the 

 control of still higher centres. If the action of the h^ad- 

 centre is suspended, the local and vegetative functions 



