vi.] ON THE STUDY OF ZOOLOGY. 103 



the scholar sees every fact for himself, and the teacher supplies only the 

 explanations. Circumstances, however, do not often allow of the attain 

 ment of that ideal, and we must put up with the next best system one in 

 which the scholar takes a good deal on trust from a teacher, who, knowing 

 the facts by his own knowledge, can describe them with so much vividness 

 as to enable his audience to form competent ideas concerning them. The 

 system which I repudiate is that which allows teachers who have not come 

 into direct contact with the leading facts of a science to pass their second 

 hand information on. The scientific virus, like vaccine lymph, if passed 

 through too long a succession of organisms, will lose all its effect in pro 

 tecting the young against the intellectual epidemics to which they are 

 exposed. 



