60 THE HUMAN BRAIN. 



ing ; just as the non-continuity of the planets with each other, and 

 the interstice between these cosmical atoms, allows and necessitates 

 their courses and revolutions. It used to be thought that nerve 

 joined and became continuous with muscle and vessel, in which case 

 thorough motion of the nervous system would not have been possible. 

 We now find that it only rests upon these lower parts, of course 

 with an interval, which allows of thorough or loco-motion ; and we 

 know, therefore, that thanks to the breathing movements, the 

 nerve animal requires to plant its foot afresh with every inspiration, 

 or it would slip down, and to raise it up again with each expiration, 

 or the body would shock it in its ascent. 



If the office of the brain lies in the distribution of the cerebral 

 fluids, then the orderly administration of these requires a regular 

 motion, or in other words, a rhythmical action. The heart and the 

 lungs are evidences of this in the lower compartment. Their action 

 is not an incorporeal vibration but a measured expansion and con- 

 traction. The blood cannot run to its destinations without the phy- 

 sical heart, nor the nerve spirit gain its ends without a propulsive 

 power in the brain and the other centres. And more than in the 

 case of the other organs must this motion belong to the brain itself, 

 or be automatic, or the supreme organ would have no function of 

 its own. It cannot, then, be derived from the heart or the lungs, 

 as we said before, although no doubt these organs, and all the rest, 

 are measured by its liberties, and concur to make its play and play- 

 ground secure. 



In the body, moreover, we find that stated motion is a condition 

 and a sign of life. Does he breathe? or expand and contract, is sy- 

 nonymous with, Does he live ? Now, as we shall have occasion to 

 show in the next chapter, the universal movement of the body pro- 

 duced by the lungs, is the condition of all particular movements, 

 muscular and visceral. For a body already in constant motion is 

 easily guided about, deflected and managed for particular motions; 

 but a body at rest absorbs a large amount of force before it can be 

 moved. Thus if the whole body were not a perpetually-moving, 

 breathing or living thing, there would lie so much dead weight on 

 the feet of every action, and life would be clogged by matter. But 

 as it is, the incarnate iron is hot for the strokes of the volitions. 



