THE HIGHER ORGANISMS 165 



not easy to localize. Little can be learned about it in 

 animals whose structure is essentially dissimilar. 



It would seem as though it must be almost universal 

 among animals as the chief means of discriminating 

 between what is useful and what is useless as food, yet 

 in this regard it is easy to fall into error for in man we 

 find the taste an unsafe guide, many things not pleasant 

 to the palate being serviceable for food and some that 

 taste quite agreeably being injurious or even poisonous. 

 It may be, therefore, that taste is not a common sense, 

 and that other means of discriminating between useful 

 and useless things are provided. However this may 

 be, when the sense exists there must be specialized nerve 

 endings to be impressed, fibres to convey these impres- 

 sions to the brain, and centres where they are to be 

 received and retained or utilized, and the fact holds 

 good that with each sense the general complexity of the 

 central nervous system is increased. 



The Central Nervous System. The greater number of 

 the special senses are situated in the cephalic region. As 

 in the usual modes of progress, whether creeping, walking, 

 flying, or swimming, the head or cephalic end of the animal 

 precedes the. rest; it is the first to come under the influence 

 of external forces, and therefore the most favorable situa- 

 tion for those "windows" through which impressions are 

 to be received. The result is quite obvious: with the 

 perfection of the organs of special sense and their correla- 

 tion with one another, the adjustment of reflexes and the 

 formation of associations, memory and the higher ner- 

 vous functions, the ganglionic masses at the cephalic 

 region come to preponderate over all others in size and 

 importance, and form the brain. 



As has been shown, the brain is important only as it 

 becomes more and more highly specialized and the seat 

 of the governing forces that control the vital functions. 

 The loss or destruction of the extremely simple brain of 

 a worm or even of a mollusk may be followed by regenera- 

 tion in part or altogether; the destruction or removal of 



