CHAPTER XXIII 



THE STOKY OF TACTILE IMPRESSIONS 



IN picturing the activities of a primitive Mammal we 

 have seen how large a share the sense of smell takes in 

 regulating the life of the animal, and in guiding it about 

 its habitat. A primitive Mammal may be said to " nose " 

 its way about the world, and it " noses " its path through 

 life in more senses than one Just as its nose leads the 

 way, and gives the first impression of novel objects by 

 permitting the animal to become acquainted with their 

 scent, so it gives the second impression of them by 

 imparting to the animal a knowledge of their " feel." 

 Such an animal is guided to an object by olfactory 

 stimuli from the nose ; afterwards, it tests the object with 

 its snout. This is a form of activity well seen among the 

 Shrews; tactile impressions of everything with which 

 they come into contact being conveyed by the elongated 

 snout. Touch tests for novel objects are carried on by 

 the extreme anterior end of the animal body in all lower 

 forms of life, and long before a " nose " is developed 

 the animal is guided through life by touching those 

 objects with which the fore-end of its moving body comes 

 into contact. When a definite nose is present, an animal 

 may be said to learn tactile experience of its surroundings 

 by bumping its nose into them. In the lower Mammals 

 this function is very obvious, and the anatomical adapta- 

 tions to subserve it are numerous. The snout region has 

 set apart for its special innervation that great ganglionated 

 cranial nerve known as the trigeminal, the branches of 

 which convey sensory impulses from the whole of the 

 skin area which surrounds the muzzle. Moreover, 

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