234 DOCTRINE OF EVOLUTION 



fulness is developing what it is worth while to bring 

 out, and inhibiting the growth of what is harmful. 

 That heredity in mental as well as in physical aspects 

 provides the varying materials with which education 

 must deal is a fundamental biological fact which is too 

 often disregarded. It would be as futile for an in- 

 structor to attempt the task of forcing the children in 

 a single schoolroom into the same mental mold, as it 

 would be for a gymnasium master to expect that by a 

 similar course of exercise he could make all of his stu- 

 dents conform to the same identical stature, the same 

 shape of the skull, or the same color of the eye and hair. 



Before leaving the subject of mental evolution we 

 must return to the conception of inseparable mind and 

 matter with which the present discussion began. The 

 whole problem of human mental evolution is solved 

 when we accept the conclusion that the nervous mech- 

 anism and the total series of its functional operations 

 have evolved together in the production of the human 

 brain and human faculty. The case regarding the 

 physical organs rests solidly on the basis of the evidences 

 outlined in a previous chapter ; the special examina- 

 tion of purely mental phenomena has likewise been 

 made in the foregoing sections. Just here we must 

 pause to give further attention to the invariable rela- 

 tion between the human mind and the human brain. 



The personality of human consciousness consists of 

 the current of thoughts and feelings flowing continu- 

 ously as one of them rises for a time to dominance only 

 to fade when it leads to and is replaced by another 



