820 ANATOMY OF VERTEBRATES. 



But from protozoa, 1 or protista, to plants and animals, the gra- 

 dation is closer than from magnetised iron to vitalised sarcode. 

 From reflex acts of the nervous system animals rise to sentient 

 and volitional ones. 



And with that ascent are associated brain-centres progressively 

 increasing in size and complexity. Arrest the development of 

 the human brain at the point it has reached in the ( Aztec,' and 

 the faculty of generalising and giving expression to such gene- 

 ralisations is wanting. The Aztecs can articulate words, and 

 apply the right noun to the thing, as e.g. e bread,' ( chair ; ' but 

 they cannot combine ideas into propositions and say f give me 

 bread,' * set me the chair.' 



For such advance in intellectual acts more brain is essential. 

 Compared with the normal state of brains in the brutes best 

 endowed, so much more cerebral substance is required, and in 

 such position, as to make the great and sudden rise, in the lowest 

 grades of man, which is referred to in p. 144. 



Thought relates to the ( brain ' of man as does electricity to the 

 nervous ( battery ' of the torpedo : both are forms of force, and 

 the results of action of their respective organs. 



Each sensation affects a cerebral fibre, and in so affecting it, 

 gives it the faculty of repeating the action, wherein memory con- 

 sists, and sensation in a dream. 



A dog at the sight of a rabbit receives a sensation which in- 

 duces a volition, and he barks with the excitement of the chase. 

 He sleeps, and by suppressed barking and agitation of limbs 

 reveals the fact that he dreams. Shall we obtain any further 

 insight into the nature of the act or acts resulting in this sensa- 

 tion, memory, dreamy imagination, by saying that the perception 

 of the rabbit reaches the ( soul ' of the dog by the affection of its 

 cerebral fibres ? Is the ( soul ' of the dog other than the per- 

 sonified sum of his psychological manifestations ? 



The ( sight ' of the dog is its faculty of vision, the ' soul ' of 

 a dog is its power of knowing what it sees and determining ac- 

 cordingly : it may approach the object with every manifestation 

 of sentiments of gladness and submissive affection : it may rush 

 upon it with every sign of rage : it may pursue it with every 

 mark of excited ardour. 



And these mental activities can only go on for a time : the 

 waste thereby occasioned of fibre and of power calls for reno- 



1 This is the better as -well as older terra : (a>ov being understood as ' life ' generi- 

 cally, and before development has differentiated its manifestations into unambiguous 

 ' vegetal ' and ' animal ' modes. 



