528 ELEMENTARY PHYSIOLOGY 



The drill had been thorough, and its effects had become 

 embodied in the man's nervous structure. 



The possibility of all education (of which military drill 

 is only one particular form) is based upon the existence of 

 this power which the nervous system possesses, of organ- 

 ising conscious actions into more or less unconscious, or 

 reflex, operations. It may be laid down as a rule, which 

 is called the Law of Association, that if any two mental 

 states be called up together, or in succession, with due 

 frequency and vividness, the subsequent production of 

 the one of them will suffice to call up the other, and that 

 whether we desire it or not. 



The object of intellectual education is to create such 

 indissoluble associations of our ideas of things, in the order 

 and relation in whicli they occur in nature ; that of a moral 

 education is to unite as fixedly the ideas of evil deeds with 

 those of pain and degradation, and of good actions with 

 those of pleasure and nobleness. 



Iiocalisation of Function in tbe Cortex of the 

 Cerebral Hemispheres. — We have already alluded (p. 525) 

 to the fact that there is a connection between particular 

 parts of the surface of the cerebral hemispheres and 

 particular acts or special sensations. The possibility thus 

 indicated is of extraordinary impoi-tance and must now be 

 dealt with in some detail. 



The cerebral hemispheres are separated along the 

 middle line of the brain by a narrow deep fissure across 

 which the corpus callosum passes as a bridge from one 

 hemisphere to the other (see Figs. 160 and 161). The 

 surface of each hemisphere is folded into a large luimber 

 of convolutions or gyri separated from each other 

 by sinuous depressions or sulci (see Fig. 159, C.C.). 

 Some of these depressions are deeper and more marked 

 than others, and are spoken of as fissures. Of these 

 the most conspicuous ai-e known as the fissure of 

 Sylvius, the fissure of Rolando, the parieto- 

 occipital fissure, and the calcarine fissure. The 



