l6o MAN, THE ANIMAL 



when he relies upon his sense organs alone. This 

 must mean that a limited amount and a selected 

 kind of activity only can normally influence man. 

 The information that comes to him through his 

 senses gives him at best an incomplete and partial 

 story of the events that are constantly going on 

 about him. It is well known that the star-nosed 

 mole has no less than 31,000 special receptors lo- 



FiGURE 54. A salamander with sense organs distributed 

 along the back, between the legs and especially on the head, 

 that are not found in the higher animals such as snakes, birds 

 and mammals. Each of these sense organs is connected with 

 the brain. Man has no way of learning just what the sensations 

 arising through stimulation of the lateral line organs, as these 

 sense organs are called, mean to a salamander. 



cated in the tip of its nose; that many aquatic ver- 

 tebrates possess numerous special receptors on the 

 head and trunk, and that insects have as many as 

 2600 receptors on the legs and wings that are be- 

 lieved to be olfactory organs. These three illus- 

 trations serve to emphasize the important fact that 

 man is limited in his receptors and that it is prob- 

 able that many animals are aware of certain forms 

 of environmental changes unappreciated by man 

 because he has no receptors for them. (Fig. 53.) 

 Thus in these limited relations of the nervous 



