84 FRAGMENTS OF SCIENCE. 



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 con- 

 summation, being an instance of the play of molecular 

 force. Given the grain and its environment, with 

 their respective forces, the purely human intellect 

 might, if sufficiently expanded, trace out a priori 

 every step of the process of growth, and, by the appli- 

 cation 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 certainly derived from the 

 food of the animal, as the motion of Trevethyck's 

 walking-engine from the fuel in its furnace. As re- 

 gards 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 



