f68 Human Physiology. 



So with the muscles that expand the lungs. No rest for them. 

 Day and night, waking and sleeping, the ribs must rise or the 

 diaphragm be drawn down, or both, until the last breath has left 

 the body. In sitting or standing many muscles are in constant 

 motion, in our unconscious balancing. 



Every movement, every expression of the countenance, is 

 made by muscular action. Smile, frown, sneer, and every 

 expression of hope, love, fear, or hate, is produced by the 

 contraction of muscular fibres, under the influence of the 

 nerves of motion, which receive their impulse from the brain, 

 the immediate organ of the soul. This is the natural language 

 of feeling and thought, and the same everywhere. There are 

 ring-like constrictor muscles to close the mouth and eyes, 

 muscles to open them, to elevate or depress the corners of the 

 mouth, and compress the nose to make all sorts of faces and 

 grimaces. There are muscles to open and shut the jaws, and 

 give them all their movements. The tongue is a mass of very 

 active and powerful muscles. 



Within the orbit, or bony case, 

 of the eye, are seven muscles. 

 One raises the eye-lid, the other 

 six give the ball of the eye all its 

 movements. In Fig. 22, 9 turns 

 the eye up, 13 draws it down, 

 Fig. 22. MUSCLES OF THE EYE- I2 > cut away, draws it to the 

 BALL, from outer side of right orbit, right, 2 to the left; and their 

 united action suffices to hold it in any position : but to perfectly 

 adapt the eye to all the requirements of vision, it needs to be 

 rotated a little on its own axis* The short muscle 8 draws it 

 one way, but for the opposite movement a longer one is 

 required; and here, as I once heard a lecturer say, "I will 

 show you a very ingenious thing on the part of the Deity." 

 The muscle 5 becomes tendinous and passes through a pulley at 

 6, and, becoming again muscular, goes back and is attached to 



