424 THE POPULAR SCIENCE MONTHLY. 



when renovation has set in, the organs generally are invigorated. 

 This is the first and most obvious consequence. It has next to be 

 qualified by the remark that human beings are unequally constituted 

 as regards the various functions; some being strong in muscle, others 

 in stomach, others in brain. In all such persons the general invigo- 

 ration is unequally shown; the favored organs receive a share pro- 

 portioned to their resjDective capitals : to him that hath shall be given. 

 Still more pertinent is the further qualification, that the organ that 

 happens to be most active at the time receives more than its share; 

 to exercise the several organs unequally is to nourish them unequally. 



To come to the point as regards our immediate object. To increase 

 the plastic projDerty of the mind you must nourish the brain. You 

 naturally expect that this result will ensue when the body generally 

 is nourished : and so it will, if there be no exorbitant demands on the 

 part of other organs, giving them such a preference as to leave very 

 little for the organ of the mind. If the digestion or the muscles are 

 unduly drawn upen, the brain will not respond to the drafts made 

 upon it. Obversely, if the brain is so constituted by nature, or so ex- 

 cited by stimulation, as to absorb the lion's share of the nutriment, 

 the opposite results will appear; the mental functions will be exalted, 

 and the other interests more or less impoverished. This is the situa- 

 tion for an abundant display of mental force. 



But we must further distinguish the mental functions themselves; 

 for these are very different and mutually exclusive. Great refinement 

 in the subdivisions is not necessary for the illustration. The broadest 

 contrast is the emotional and the intellectual feeling as pleasure, 

 pain, or excitement, and feeling as knowledge. These two in extreme 

 manifestation are hostile to each other: under extreme emotional 

 excitement the intellect suffers ; under great intellectual exertion the 

 emotions subside (with limitations unnecessary for our purpose). 



But intellect in the largest sense is not identical with the reten- 

 tive or plastic operation. The laws of this peculiar phase of our in- 

 telligence are best obtained by studying it as a purely mental fact. 

 Yet there is a physiological way of looking at it that is strongly con- 

 firmative of our psychological observations. On the physical or 

 physiological side, memory or acquisition is a series of new nervous 

 growths, the establishment of a number of beaten tracks in certain 

 lines of the cerebral substance. Now, the presumption is that, as 

 regards the claim for nourishment, this is the most costly of all the 

 processes 'of the intelligence. To exercise a power once acquired 

 should be a far easier thing, much less expensive, than to build up a 

 new acquirement. We may be in sufficiently good condition for the 

 one, while wholly out of condition for the other. Indeed, success in 

 acquirement, looking at it from the physiological probabilities, should 

 be the work of rare, choice, and happy moments ; times when cerebral 

 vi<jor is both abundant and well-directed. 



