130 MECHANISM OF THE MUSCLES. 



so well to place a muscle, or bring it to act in the 

 usual way. For example. A muscle is necessary 

 to draw down the lower jaw, and this is done by 

 a muscle inserted above the jaw. Nothing is more 

 common in mechanics, than pulling one way to make 

 the object move in the very opposite. But then the 

 rope must pass through a ring or pulley. The sai- 

 lor pulls down, and the cask comes up. He has 

 a pulley above through which his rope is roven. The 

 same contrivance is adopted in the present instance; 

 the muscle called the digastric muscle, descends from 

 the side of the head, and passes through a loop in 

 the neck below the jaw whence it ascends and is at- 

 tached to the part to be drawn. 



Fig. 22. 



a, the digastric muscle, which is represented as coming down and 

 passing through a slit or ring in another muscle indicated by 

 the line b. After leaving the ring where it is formed into a 

 round, strong tendon, it again becomes fleshy, runs upward, 

 and is inserted into the chin to draw the jaw down, c, is a 

 bone called the os-hyoides, which seems to operate as a stay 

 or brace ; the muscle containing the loop is fastened at d. 



