3i6 



NATURE 



\Aitg. 20, 1874 



appiopriate detail, placing it in its proper relations, and usually 

 giving it a significance which, as long as it was kept isolated, 

 failed to appear. This is done without a trace of ill-temper, 

 lie moves over the subject with the passionless strength of a glacier ; 

 and the grinding of the rocks is not always without a counterpart 

 in the logical pulverisation of the objector. But though in 

 handling this mighty theme all passion has been stilled, there is 

 an emotion of the intellect incident to the discernment of new 

 truth which often colours and warms the pages of Mr. Darwin. 

 Ilis success has been great ; and this implies not only the 

 solidity of his work, but the preparedness of the public mind for 

 such a revelation. On this head a remark of Agassiz impressed 

 me more than anything else. Sprung from a race of theologians, 

 this celebrated man combated to the last the theory of natural 

 selection. One of the many times I had the pleasure of meeting 

 him in the United States was at Mr. Winthrop's beautiful resi- 

 dence at Brookline, near Boston. Rising from luncheon, we all 

 halted as if by a common impulse in front of a window, and 

 continued there a discussion which had been started at table. 

 The maple %vas in its autumn glory ; and the exquisite beauty of 

 the scene outside seemed, in my case, to interpenetrate without 

 disturbance the intellectual action. Earnestly, almost sadly, 

 Agassiz turned and .said to the gentlemen standing round, "I 

 confess that I was not prepared to see this theory received as it 

 has been by the best intellects of our time. Its success is greater 

 than I could h.ave thought possible." 



In our day great generalisations have been reached. The 

 theory of the origin of species is but one of them. Another, of 

 still wider grasp and more radical significance, is the doctrine of 

 the Conservation of Energy, the ultimate philosophical issues of 

 which are as yet but dimly seen — that doctrine which "binds 

 nature fast in fate " to an extent not hitherto recognised, exacting 

 from every antecedent its equivalent consequent, from every con- 

 sequent its equivalent antecedent, and bringing vital as well as 

 physical phenomena under the dominion of that law of causal 

 connection which, as far as the human understanding has yet 

 pierced, asserts itself everywhere in nature. Long in advance of 

 all definite experiment upon the subject, the constancy and in- 

 destructibility of matter had been affirmed ; and all subsequent 

 experience justified the affirmation. Later researches extended 

 the attribute of indestructibility to force. This idea, applied in 

 the first instance to inorganic, rapidly embraced organic nature. 

 The vegetable world, though drawing almost all its nutriment 

 from invisible sources, was proved incompetent to genei'ate anew 

 either matter or force. Its matter is for the most part trans- 

 muted air ; its force transformed solar force. The animal world 

 was proved to be equally uncreative, all its motive energies being 

 referred to the combustion of its food. The activity of each 

 animal as a whole was proved to be the transfened activities of 

 its molecules. The muscles were shown to be stores of mecha- 

 nical force, potential until unlocked by the nerves, and then re- 

 sulting in muscular contractions. The speed at which messages 

 fly to and fro along the nerves was determined, and found to be, 

 not as had been previously supposed, equal to that of light or 

 electricity, but less than tlie speed of a flying eagle. 



This was the work of the physicist : then came the conquests 

 of the comparative anatomist and physiologist, revealing the 

 structure of every animal, and the function of every organ in the 

 whole biological series, from the lowest zoophyte up to man. 

 The nervous system had been made the object of profound and 

 continued study, the wonderful and, at bottom, entirely mys- 

 terious controlling power which it exercises over the whole 

 organism, physical and mental, being recognised more and more. 

 Thought could not be kept back from a subject so profoundly 

 suggestive. Besides the physical life dealt with by Mr. Darwin, 

 there is a psychical life presenting similar gradations, and asking 

 equally for a solution. How are the different grades and orders 

 of mind to be accounted for ? What is the principle of growth 

 of that mysterious power which on our planet culminates in 

 Reason ? These are questions which, though not tlirusting them- 

 selves so forcibly upon the attention of the general public, had 

 not only occupied many reflecting nrinds, but liad been formally 

 broached by one of them before the "Origin of Species" 

 appeared. 



With the mass of materials furnished by the physicist and 

 physiologist in his hands, Mr. Herbert Spencer, twenty years 

 ago, sought to graft upon this basis a system of psychology ; 

 and two years ago a second and greatly amplified edition of his 

 work appeared. Those who have occupied themselves with the 

 beautiful experiments of Plateau, will remember that when two 

 spherules of olive-oil suspended in a mixture of alcohol and 



water of the same density as the oil, are brought together, they 

 do not immediately unite. Something like a pellicle appears to 

 be formed around the drops, the rupture of which is immediately 

 followed by the coalescence of the globules into one. There 

 are organisms whose vita! actions are almost as purely physical 

 as that of these drops of oil. They come into contact and fuse 

 themselves thus together. From such organisms to others a 

 shade higher, and from these to others a shade higher still, and 

 on through an ever-ascending series, Mr. Spencer conducts his 

 argument. There are two obvious factors to be here taken 

 into account — the creature and the medium in which it lives, or, 

 as it is often expressed, the organism and its environment. Mr. 

 Spencer's fundamental principle is, that between these two 

 factors there is incessant interaction. The organism is played 

 upon by the environment, and is modified to meet the require- 

 ments of the environment. Life he defines to be "a continuous 

 adjustment of internal relations to external relations. 



In the lowest organisms we have a kind of tactual sense 

 diffused over the entire body ; then, through impressions from 

 without and their corresponding adjustments, special portions of 

 the surface become more responsive to stimuli than others. Tlie 

 senses are nascent, the basis of all of them being that simple 

 tactual sense which the sage Democritus recognised 2,300 years 

 ago as their common progenitor. The action of light, in the 

 first instance, appears to be a mere disturbance of the chemical 

 processes in the animal organism, similar to that which occurs 

 in the leaves of plants. By degrees the action becomes localised 

 in a few pigment-cells, more sensitive to light than the surround- 

 ing tissue. The eye is here incipient. At first it is merely 

 capable of revealing differences of light and shade produced by 

 bodies close at hand. Followed as the interception of the light 

 is in almost all cases by the contact of the closely adjacent opaque 

 body, sight in this condition becomes a kind of "anticipatory 

 touch." The adjustment continues ; a slight bulging out of the 

 epidermis over the pigment-granules supervenes. A lens is in- 

 cipient, and, through the operation of infinite adjustments, at 

 length reaches the perfection that it displays in the hawk and the 

 eagle. So of the other senses ; they are special differentiations 

 of a tissue which was originally vaguely sensitive all over. 



With the development of the senses the adjustments between 

 the organism and its environment gradually extend in space, a 

 multiplication of experiences and a corresponding modification 

 of conduct being the result. The adjustments also extend in 

 time, covering continually greater intervals. Along with this 

 extension in space and time, the adjustments also increase in 

 speciality and complexity, passing through the various gradis of 

 brute life and prolonging themselves into the domain of reason. 

 Very striking are Mr. Spencer's remarks regarding the influence 

 of the sense of touch upon the development of intelligence. 

 This is, so to say, the mother-tongue of all the senses, into which 

 they must be translated to be of service to the organism. Hence 

 its importance. The parrot is the most intelligent of birds, and 

 its tactual power is also greatest. From this sense it gets know- 

 ledge unattainable by birds which cannot employ their feet as 

 hands. The elephant is the most sagacious of quadrupeds — its 

 tactual range and skill, and the consequent multiplication of 

 experiences, which it owes to its wonderfully adaptable trunk, 

 being the basis of its sagacity. Feline animals, for a similar 

 cause, are more sagacious than hoofed animals — atonement being 

 to some extent made, in the case of the horse, by the possession 

 of sensitive prehensile lips. In the I'lintatcs the evolution of 

 intellect and the evolution of tactual appendages go hand in 

 hand- In the most intelligent anthropoid apes we find the 

 tactual range and delicacy greatly augmented, new avenues of 

 knowledge being thus opened to the animal. Man crowns the 

 edifice here, not only in virtue of his own manipulatory power, 

 but through the enormous extension of his range of experience, 

 by the invention of instruments of precision, which serve as 

 supplemental senses and supplemental limbs. The reciprocal 

 action of these is finely described and illustrated. That dias- 

 tened intellectual emotion to which I have referred in connection 

 with Mr. Darwin is, I should say, not absent in Mr. Spencer. 

 His illustrations possess at times exceeding vividness and force, 

 and from his style on such occasions it is to be inferred that the 

 ganglia of this apostle of the understanding are sometimes the 

 seat of a nascent poetic thrill. 



It is a fact of supreme importance that actions, the perform- 

 ance'of which at first requires even painful effort and deliberation, 

 may by habit be rendered automatic. Witness the slow learning 

 of its letters by a child, and the subsequent facility of reading in 

 a man, when each group of letters M'hich forms a word is instantly 



