334 NATURAL THEOLOGY. 



water to the hand : the effect of the motion of the 

 marble upon the surrounding water. 



With respect to the semicircular canals above 

 described, I am at a loss to understand what is 

 meant by some authors saying that their use is not 

 known. These canals consist of an elastic mem- 

 brane full of fluid, with a nerve suspended upon 

 the septum of one extremity : are they not then 

 admirably suited to receive the impulses which 

 are conveyed through the bones of the head? 

 That they are so, is clear from their being found 

 in the heads of fishes, where there is no access of 

 vibration to the nerve, except through the bone. 

 But we are affected by the same when our head 

 is on the pillow and we are awakened by people 

 moving in the house : the alarm is through the 

 solid bones of the head. And when the Indian 

 puts his ear to the ground to hear a distant tread, 

 he is substituting the communication through the 

 solids and the bones of the head for the atmosphe- 

 ric impulses. 



Again, let us recur to the proposition that sound 

 is propagated to the internal ear in two ways : 

 through the chain of bones and fenestra ovalis into 

 the vestibule, and also through the air of the tym- 

 panum, and by the fenestra rotunda into the coch- 

 lea. There appear strong objections to this doc- 

 trine. It declares the chain of bones and their 

 appended muscles and beautiful articulations to 

 be altogether useless ; for if the sound can be com- 

 municated through the air of the tympanum, what 



