6^(i THE POPULAR SCIENCE MONTHLY. 



vegetable world, though drawing almost all its nutriment from invisi- 

 ble sources, was proved incompetent to generate anew either matter 

 or force. Its matter is for the most i)art transmuted 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 transferred activities of its molecules. The muscles were shown 

 to be stores of mechanical force, potential until unlocked by the nerves, 

 and then resulting in muscular contractions. The speed at which mes- 

 sages 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 electri- 

 city, bnt less than the 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 biologi- 

 cal series, from the lowest zoophyte up to man. The nervous system 

 had been made the object of profound and continued study, the won- 

 derful and, at bottom, entirely mysterious controlling power which it 

 exercises over the whole organism, physical and mental, being recog- 

 nized more and more. Thought could not be kept back from a sub- 

 ject 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 diflferent 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 thrusting themselves so forci- 

 bly upon the attention of the general public, had not only occupied 

 many reflecting minds, but had been formally broached by one of them 

 before the " Origin of Species " appeared. 



With the mass of materials furnished by the physicist and physi- 

 ologist 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 imme- 

 diately followed by the coalescence of the globules into one. There 

 are organisms whose vital actions are almost as purely physical as 

 til at 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 hicjher still, and on throuoh 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 



