MICROSCOPIC BRAINS. 11 



experiences of his ancestors have made that 

 lobe enormously developed. But in a man's 

 head you would find a very large and fine 

 optic centre, and only a mere shrivelled relic 

 to represent the olfactory lobes. You and I 

 and our ancestors have had but little occasion 

 for sniffing and scenting ; our sight and our 

 touch have done duty as chief intelligencers 

 from the outer world ; and the nerves of smell, 

 with their connected centres, have withered 

 away to the degenerate condition in which 

 they now are. Consequently, smell plays but 

 a small part in our thought and our memories. 

 The world that we know is chiefly a world 

 of sights and touches. But in the brain of 

 dog, or deer, or antelope, smell is a prevail- 

 ing faculty; it colours all their ideas, and it 

 has innumerable nervous connections with 

 every part of their brain. The big olfac- 

 tory lobes are in direct communication 

 with a thousand other nerves ; odours rouse 

 trains of thought or powerful emotions in 

 their minds just as visible objects do in our 

 own. 



