974 Dynamic Theory. 



The axiom is the lowest term of perception that can exist, as perception. 

 Analyze it further and we get no longer perceptions but their antece- 

 dent elemental sensations. The sensation being simple it cannot be an- 

 alyzed, but traced to its antecedent cause we have no longer sensation 

 but another form of molecular motion. 



If all bodies were of a uniform nature, constitution and form, there 

 is no reason to suppose that there would be different modes of motion. 

 When a cannon is discharged, the force of the explosion drives the ball 

 in one direction and the gun in the other. But the characters of the 

 movements of these two are in striking contrast, owing to their differ- 

 ence in form, mass, &c. So the same wind causes the fluttering of the 

 flag at the mast head, the whistling and roaring music of the rigging, 

 and the undulations of the briny waves, the differences in motion ob- 

 viously due to the differences in the bodies moved. And in each case 

 we know that the several motions represent an amount of energy ab- 

 stracted from that of the moving wind, the force of which is reduced 

 by that much. So when we see a molecular motion outside of the 

 body setting up a different sort of motion inside of it, we are justified 

 in concluding that the cause of the change in the form of the motion is 

 the difference in the form of the body moved. In other words the rea- 

 son why a peculiar undulation of ether sets up the motion called red, is 

 because the small quantity of ether in the brain cell is under different 

 conditions from that outside. And the further deduction is legitimate, 

 that when protoplasm is organized into the peculiar forms of nervous 

 and ganglionic tissues, it is susceptible to the motions called sensations; 

 and further still, that the action of external molecular energy upon pro- 

 toplasm tends to thus organize it. 



It is easy to see that there are great differences in degrees of sensi- 

 bility. The tissues involved, like those involved in muscle movement, 

 are wasted by the exercise of their function, and are repaired by renew- 

 als from the blood. As in the case of the muscles too, the renewals 

 may exceed the losses and the tissues grow into better working condi- 

 tions. This, as observed in the case of the muscles, is no doubt pro- 

 moted by the greater energy that characterizes the chemical reactions 

 when the elements are in the nascent state, as they are after being forci- 

 bly freed from a former combination. ( See page 498. ) It is also pro- 

 moted, as pointed out by H. Spencer, by an increase in the capacity of 

 the blood vessels, which takes place on account of the extra amount of 

 blood demanded and forced through them during continued and steady 

 moderate work, by which increase the quantity of blood delivered will 

 continue to be greater, and thus the organ so nourished gain in size and 

 force. The same law of gain from being operated, governs in the case 

 of the nervous and brain cell tissues, as we all know by experience, and 



