5*20 THE MECHANICAL FUNCTIONS. 



with lightness ; the plates which form their sides 

 being disposed in a radiated manner towards the 

 circumference, and arranged with great regu- 

 larity ; and the cells themselves, instead of con- 

 taining marrow, are filled with air, by means of 

 communications with the Eustachian tubes, 

 which open into the nostrils : thus a great 

 extent of surface is given to the skull, without 

 any addition to its weight. The ligamentum 

 nuchae also comes in aid of the muscular power, 

 being here of vast size and strength. 



The head being limited in its range of motion 

 by its approximation to the trunk, the mouth 

 cannot be applied directly to seize the food : and 

 some means were therefore to be provided for 

 bringing the food to the mouth. For this pur- 

 pose a new organ, the proboscis, has been con- 

 structed : it consists of a cylinder, perfectly 

 flexible, and of a length sufficient to reach the 

 ground, when the elephant is standing. The 

 animal has the power of moving it in all possible 

 directions by means of a prodigious number of 

 muscular fibres, which are collected in small 

 bands, some passing transversely, and radiating 

 from the interior towards the circumference, 

 others situated more obliquely, and a third set 

 running longitudinally, and forming an exterior 

 layer : but they are all variously interlaced 

 together so as to compose a very complicated 

 arrangement. The extremity of the proboscis. 



