104 HUMAN PHYSIOLOGY 



comprehensive view be taken of the functions of 

 any nervous system, whether in lower or in higher 

 /forms, we might define it as a particular series of 

 j organs in an animal body set apart for the purpose 

 \of exercising the function of Relation. By this latter 

 term is implied the bringing of the living being into 

 " relation " with the world in which it lives. Apart 

 from the possession of a nervous system or its 

 equivalent in the lowest forms, the living being 

 would be incapable of reacting upon the impressions 

 received from the outer world. It would, in other 

 words, be a non-sensitive thing, and it might, there- 

 fore, take rank with inorganic or non-living objects. 

 All living things may be regarded as possessing a 

 definite amount of sensitiveness, and this opinion 

 holds good for the lowest animals, and also for 

 plants in which no trace of nervous system has as 

 yet been discovered. But as living matter itself is 

 everywhere sensitive, we can understand that in the 

 absence of a nervous apparatus, a small speck of 

 living matter constituting the body of a lower 

 animal, exercises the function of sensation, is able to 

 feel the contact of food particles, and to act upon 

 the impressions to which the contact with these 

 particles gives rise. From this view of the 

 nervous system we may advance to yet another 

 generalisation of some service in enabling us to 

 understand the difference between a nervous system 

 of low degree and one of high degree. The higher 

 nervous system of animals possesses a more perfect 

 and intimate relationship developed between its 

 possessor and the world in which it lives. Take, for 

 example, the acts of a highly organised brain and 

 nervous system which a dog posesses. It is capable 

 of exercising a high degree of intelligence, yet it falls 



