September 21, 1893] 



NA TURE 



S<>5 



placed at the upper end of the vertebral column, and encased in a 

 complete osseous covering called the skull. We liarn from 

 I numerous experimental researches, carried out by physiologists 

 in recent years, that the brain is a dual organ, consisting of a 

 ^ double series of distinct ganglia and connected to some extent 

 \ by a complex system of nervous tissues, not only with each 

 other, but with the central seat of consciousness and volition. 

 j But the difficulty of determining the nature of its functions, and 

 I the modus af'eiaiidi of its psychological manifestations, is so 

 ! great that I must pass over this part of the subject very lightly 

 j indeed. The conditions of ordinary reflex-action require that a 

 group of muscles, by means of which a particular bodily move- 

 ment is eflfected, shall be connected with its co-ordinating gang- 

 lion by an alTerent and an efferent system of nerves. Impressions 

 from without are conveyed by the former, or sensory nerves, to 

 the central ganglion, fioni which an impulse is retransmitted by 

 the motor nerves and sets in operation the muscular force for 

 i producing the required movement. But this efferent message 

 j is, in many cases, absolutely controlled by volition, and not only 

 j can it prevent the muscular action from taking place, but it 

 cin effect a similar movement, de novo, without the direct inter- 

 I vention of external impressiims at all. Now it has been proved 

 experimentally that the volitional stimulus, which regulates the 

 I various movements of the body, starts from definite portions of 

 : ihe brain according to the different results to be produced. This 

 ; localisation of brain functions, though still far from being 

 thorouglily understood, comes very appropriately into use in 

 I this inquiry. From it we learn that the homology which charac- 

 ' lerises the structural elements of the bodies of animals extends 

 also to the component parts of their respective brains. The law 

 , which differentiates animals according to the greater special- 

 ; iiation of the functions of their various organs has therefore its 

 I counterpart in the brain, and we naturally expect an increase of 

 I brain substance in every case in which the functional activity of 

 a specific organ i-i extended. Thus the act of stitching with a 

 needle and thread, an act beyond the mental and physical capa- 

 city of any animal but man, would entail a certain increase of 

 I brain substance, simply in obedience to the great complexity of 

 the movements involved in its execution, over and above that 

 which may be supposed to be due to the intellectual and reason- 

 ing faculties which invented it. 



That man's brain and his intelligence are correlated to each 

 other is a fact too axiomatic to require any demonstration ; nor 

 can it be doubted that the relaiionship f>etween them is of the 

 j nature of cause and effect. But to maintain that the amount of 

 ]the latter is directly proportional to the size of the former is 

 ^rather straining. the laws of legitimate inference. In drawing 

 |any general conclusion of this nature from the bulk of brain 

 j.substance, there are some modifying influences which cannot be 

 :dcsregarded, such, for example, as the amount of cranial cir- 

 jculation and the quality of the brain cells. But the deter- j 

 jmination of this point is not the exact problem with which the | 

 ievoliitioni>t is primarily concerned. To him the real crux in the i 

 'inquiry is to account for the evolution of man's comparatively 

 jlarge brain under the influence of existing cosmic forces. 

 Alter duly considering this prol>lem, and casting about for a 

 'possible explanation, I have come to the conclusion that not 

 pnly is it the result of natural laws, but that one of the main 

 j'actors in its production was the conversion of the upper limbs 

 into true hands. From the first moment that man recognised 

 I he advantage of using a club or a stone in attacking his prey or 

 defending hmiself from his enemies, the direct incentives to a 

 'ligher brain development came into existence. He would soon 

 ,earn by experience that a particular form of club or stone was 

 inoie suitable for his purposes; and if the desiderated object 

 vere not to be found among the natural materials around him, 

 iie would proceed to manufacture it. Certain kind-; of stoues 

 jvould be readily recognised as better adapted for cutting pur- 

 l>oses than others, and he would select his materials accordingly, 

 f these were to be found only in a special locality, he would 

 ji-il that locality whenever the prized material was needed. Nor 

 jirould it lie an unwarrantalde stretch of imagination to suppose 

 .h,it the circumstances would lead him to lay up a store for future 

 These simple acts of intelligence assume little more than 

 . be seen in the actions of many of the lower animals. Con- 

 jCiousne.ss of his power to make and to wield a weapon was a new 

 jeparlurein the career of man, and every repetition of such acts 

 ,ecame an effective an<l ever-accumulating training force. What 

 j memorable event in the history of hu nanity was the manufac- 

 jre of the first shai-p stone implement ! Our sapient ancestor, 



NO. 1247, VOL. 48] 



who first used a spear tipped with a sharp flint, became pos- 

 sessed of an irresistible power over his fellow men. The inven- 

 tion of the bow and arrow may be paralleled with the discovery 

 of gunpowder and the use of cannon, both of which revolution- 

 ised the principles of warfare in their respective ages. The art 

 of making fire had a greater influence on human civilisation than 

 the modern discovery of electricity. The first boat was in all 

 probability a log — an idea which might have been suggested by 

 the sight of an animal clinging to a fljitin^ piece of wood car- 

 ried away by a flood. To scoop this log into a hollow boat 

 was an afterthought. The successive increments of know- 

 ledge by which a single-tree canoe has been transformed into 

 a first-class Atlantic liner are scattered through the unwritten 

 and written annals of many ages. In his expeditions for hunt- 

 ing, fishing, fruit-gathering, &c., primitive man's acquaint- 

 ance with the mechanical powers of nature would be gradually 

 extended, ami pari passu with the increasing range of his know- 

 ledge there would be a corresponding development in his reason- 

 ing faculties. Natural phenomena suggested reflections as to 

 their causes and effects, and so by degree? they were brought 

 into the category of law and order. Particular sounds would be 

 used to represent specific objects, and these would become the 

 first rudiments of language. Thus each generalisation when 

 added to his previous little stock of kno.v ledge widened the 

 basis of his intellectual powers, and as the process progressed 

 man would acquire soaie notion of the abstract ideas of space, 

 time, motion, force, number, &c. ; and continuous thought and 

 reasoning w-^uld ultimately become habitual to him. All these 

 mental operations could only take place through the medium of 

 additional nerve cells, and hence the brain gradually became 

 more bulky and more complex in its structure. Thus the func- 

 tions of the hand and of the brain have been correlated in a 

 most remarkable manner. Whether the mechanical skill of the 

 hand preceded the grea'er intelligence of the brain, or -vice 

 versa, I will not pretend to say. Bat between the two there 

 must have been a constant interchange of gifts. According to 

 Sir C. Bell, "the hand supplies all instruments, and by its 

 correspondence with the intellect gives him universal dominion." 

 ("The Hand," &c. " Bridgewater Treatise," p. 38.) 



That mind, in its higher psychical manifestations, has some- 

 times been looked upon as a spiritual essence which can exist 

 separately from its material basis need not be wondered at when 

 we consider how the pleasing abstractions of the poet, or the 

 fascinating creations of the novelist, roll out, as it were, from a 

 hidden cavern without the slightest symptom of physical action. 

 It is this marvellous power of gathering and combining ideas, 

 previously derived through the ordinary senses, which gives a 

 primA facie appearance of having here to deal with a force 

 exterior to the brain itself. But indeed it is questionable if such 

 psychological phenomena are really represented by special 

 organic equivalents. May they not be due rather to the power 

 of volitional reflection which summons them from the materials 

 stored up by the various localised portions into which the brain 

 is divided? From this point of view there may be many 

 phases of pure cerebration which, though not the result of 

 direct natural selection, have nevertheless as natural and physical 

 an origin as conscious sensation. Hence imagination, concep- 

 tion, idealisation, the moral faculties, &o., may be compared to 

 parasites which live at the expense of their neighbours. After 

 all the greatest mystery of life lies in the simple acts of con- 

 scious sensation, and not in the higher mental combinations into 

 which they enter. The highest products of intellectuality are 

 nothing more than the transformation of previously existing 

 energy, and it is the power to utilise it that alone finds its special 

 organic equivalent in the brain. 



But this brings us on controversial ground of the highest 

 importance. Prof. Huxley thus expresses his views on the 

 phase of the argument now at issue : — 



" I have endeavoured to show that no absolute structural line 

 of demarcation, wider than that between the animals which 

 immediately succeed us in the scale, can be drawn between the 

 animal world and ourselves ; and I may add the expression of 

 my belief that the attempt to draw psychical distinction is equally 

 futile, and that even the highest faculties of feeling and of intel- 

 lect begin to germinate in lower forms of life." (" Evidences as 

 to Man's Place in Nature," p. 109.) 



On the other hand, Mr. Alfred K. Wallace, who holds such 

 a distinguished position in this special field of research, has 

 promulgated a most remarkable Jlheory. This careful investi- 

 gator, an original discoverer of the laws of natural selection, and 



