TOUCH — GENERAL II5 



in the beak; this is turned round and shifted about by 

 means of the sense of touch centred in the tongue. So dehcate 

 is this sense that the huge massive beaks of macaws are able 

 to deal with very small seeds — even canary seed — from 

 which they can remove the husk. This is an operation that 

 would defy the comparatively clumsy hands of a human 

 being. 



Woodpeckers, too, with their long tubular tongues, barbed 

 at the tip, can "feel" the grubs moving in the tunnels which 

 they have made in trees. Once located in this way, the flexi- 

 bility and the barbs on the tongue enable the woodpeckers 

 to extract the grubs safely and accurately. 



Those puzzling bristles at the sides of the mouths of night- 

 jars are thought, by some workers, to be organs of touch 

 even though they may also serve to catch up moth scales 

 from victims caught on the wing. The nightjar also has a 

 claw-comb which it uses to keep these bristles clean after a 

 meal. Such combs are found on other birds, and although 

 they are modified claws, they are certainly capable of some 

 degree of sensitiveness to touch. The whiskers with which 

 many mammals are provided are also very sensitive tactile 

 features. 



As far as sensations are concerned, we come across these 

 in many cold-blooded animals. The fact that these types of 

 creature are dependent on the temperature of the surround- 

 ings for activity, shows that they must have specialized nerves 

 which can convey impressions of warmth or cold all over the 

 body. 



The "pit vipers", represented so well by the rattlesnakes, 

 are so called on account of the pits (which look like holes) 

 on each side of the head and situated between the eyes and 

 the nostrils. These are now thought to be sense organs which 

 can register temperature, and are used as additional detectors 

 of warm-blooded prey. 



Fish, as has already been mentioned, are very sensitive to 

 vibrations in the water, and the delicate nervous system 

 connected with the lateral line is considered to be the means 

 by which fishes can feel currents and other vibrations — 

 another example of tactile sense. 



In the insects, certain hairs on the bodies and limbs are 



