NATURAL THEOLOGY. 151 



dener will do more execution, by being able to carry 

 his scithe, his rake, or his flail, with a sufficient des- 

 patch through a sufficient space, than if, with 

 greater strength, his motions were proportionably 

 more confined and slow. It is the same with a 

 mechanic in the use of his tools. It is the same 

 also with other animals in the use of their limbs. 

 In general, the vivacity of their motions would be 

 ill exchanged for greater force under a clumsier 

 structure. 



We have offered our observations upon the 

 structure of muscles in general; w^e have also no- 

 ticed certain species of muscles; but there are 

 also single muscles which bear marks of mecha- 

 nical contrivance appropriate as well as particular. 

 Out of many instances of this kind we select the 

 following : — 



I. Of muscular actions, even of those which are 

 well understood, some of the most curious are in- 

 capable of popular explanation ; at least without 

 the aid of plates and figures. This is in a great 

 measure the case with a very familiar, but, at the 

 same time, a very complicated motion, that of the 

 lower jaw ; and with the muscular structure by 

 which it is produced. One of the muscles con- 

 cerned may, however, be described in such a 

 manner as to be, I think, sufficiently comprehend- 

 ed for our present purpose. The problem is to 

 pull the low^er jaw down. The obvious method 

 should seem to be, to place a straight muscle — 

 viz., to fix a string from the chin to the breast, the 



