

MAN 313 



are two great swellings on the dorsal surface of the brain: 

 the cerebrum, which is the seat of " voluntary" activity, 

 consciousness, memory, and reason; and the cerebellum in 

 which reside many of the centers for controlling the strength 

 and steadiness of muscular activity. There are other ad- 

 justor groups of nerve cells in the brain, spinal cord, and 

 among the internal organs. These for the most part con- 

 trol simple reflexes in organs near them. 



The nervous activities of man are remarkable in two re- 

 spects: (1) a vast number of practically unvarying and 

 more or less automatic reflexes (which greatly exceeds that 

 of other animals, except perhaps birds) is controlled by the 

 nerve centers in certain regions of the brain outside the 

 cerebrum and in the spinal cord; those concerned with the 

 vital functions of the internal organs being dominated by 

 certain parts of the brain (medulla, etc.), and those con- 

 cerned with instinctive reactions of the skeletal muscles 

 being largely controlled in the cord. (2) The higher men- 

 tal faculties concerned with variable activities are developed 

 as in no other animal. The enormous system of branching 

 nerve cells in the outside layer of the cerebrum makes pos- 

 sible, not only the proper adjustment of the body to condi- 

 tions as reported by effectors, but the storing of sensory 

 memories upon which knowledge and the power of reason- 

 ing depend. 



At birth a child has the main tracts in its nervous system 

 formed, but is able during youth to strengthen or con- 

 trol its natural endowment by training. It may be natur- 

 ally " bright" in solving mathematical problems, or "dull" 

 in languages; awkward or graceful; docile or stubborn. 

 Youth is the golden time for improvement, for there comes 

 a day when the fiber tracts are no longer modifiable. As 

 Herrick puts it, "the docile period is past, and though the 

 man may continue to improve in the technic of his per- 

 formance, he can no longer do creative work. Whether 

 this process occurs at the age of twenty or eighty years, it 

 is the beginning of senility. And, alas, this coagulation of 



