LECTURES AND ESS A YS 



beginning to end. It would see every 

 molecule placed in its position by the 

 specific attractions and repulsions exerted 

 between it and other molecules, the 

 whole process, and its consummation, 

 being an instance of the play of molecular 

 force. Given the grain and its environ- 

 ment, with their respective forces, the 

 purely human intellect might, if suffi- 

 ciently expanded, trace out a priori 

 every step of the process of growth, and, 

 by the application of purely mechanical 

 principles, demonstrate that the cycle 

 must end, as it is seen to end, in the 

 reproduction of forms like that with 

 which it began. A necessity rules here, 

 similar to that which rules the planets 

 in their circuits round the sun. 



You will notice that I am stating the 

 truth strongly, as at the beginning we 

 agreed it should be stated. But I must 

 go still further, and affirm that in the 

 eye of science the animal body is just as 

 much the product of molecular force as 

 the chalk and the ear of corn, or as 

 the crystal of salt or sugar. Many of 

 the parts of the body are obviously 

 mechanical. Take the human heart, for 

 example, with its system of valves, or 

 take the exquisite mechanism of the eye 

 or hand. Animal heat, moreover, is 

 the same in kind as the heat of a fire, 

 being produced by the same chemical 

 process. Animal, motion, too, is as cer- 

 tainly derived from the food of the 

 animal as the motion of Trevethyck's 

 walking-engine from the fuel in its fur- 

 nace. As regards matter, the animal 

 body creates nothing ; as regards force, 

 it creates nothing. Which of you by 

 taking thought can add one cubit to his 

 stature? All that has been said, then, 

 regarding the plant may be restated with 

 regard to the animal. Every particle 

 that enters into the composition of a 

 nerve, a muscle, or a bone has been 

 placed in its position by molecular force. 

 And unless the existence of law in these 

 matters be denied, and the element of 

 caprice introduced, we must conclude 

 that, given the relation of any molecule 

 of the body to its environment, its posi- 



tion in the body might be determined 

 mathematically. Our difficulty is not 

 with the quality of the problem, but with 

 its complexity ; and this difficulty might 

 be met by the simple expansion of the 

 faculties we now possess. Given this 

 expansion, with the necessary molecular 

 data, and the chick might be deduced 

 as rigorously and as logically from the 

 egg as the existence of Neptune from 

 the disturbances of Uranus, or as conical 

 refraction from the undulatory theory of 

 light. 



You see I am not mincing matters, but 

 avowing nakedly what many scientific 

 thinkers more or less distinctly believe. 

 The formation of a crystal, a plant, or 

 an animal is, in their eyes, a purely 

 mechanical problem, which differs from 

 the problems of ordinary mechanics in 

 the smallness of the masses, and the 

 complexity of the processes involved. 

 Here you have one half of our dual 

 truth; let us now glance at the other 

 half. Associated with this wonderful 

 mechanism of the animal body we have 

 phenomena no less certain than those of 

 physics, but between which and the 

 mechanism we discern no necessary con- 

 nection. A man, for example, can say 

 "I feel," "I think," "I love"; but how 

 does consciousness infuse itself into the 

 problem ? The human brain is said to 

 be the organ of thought and feeling : 

 when we are hurt, the brain feels it ; 

 when we ponder, or when our passions 

 or affections are excited, it is through 

 the instrumentality of the brain. Let us 

 endeavour to be a little more precise 

 here. I hardly imagine there exists a 

 profound scientific thinker, who has 

 reflected upon the subject, unwilling to 

 admit the extreme probability of the 

 hypothesis, that for every fact of con- 

 sciousness, whether in the domain of 

 sense, thought, or emotion, a definite 

 molecular condition, of motion or struc- 

 ture, is set up in the brain ; or who 

 would be disposed even to deny that, if 

 the motion, or structure, be induced by 

 internal causes instead of external, the 

 effect on consciousness will be the same? 



