THE MUSCLES. 61 



from the breast-bone to the knob behind the ear. Its effect is to bend 

 the face forward, turning it at the same time to the other side ; and 

 when the muscles of the two sides act together, they simply bend 

 the neck forward. Above and in front of this one, are seen three 

 narrow strap-shaped muscles, which pull down the windpipe, as in 

 singing the lower notes of the scale. Higher up, three small mus- 

 cles are seen attached also to the windpipe, and in front to the jaw, 

 which have the opposite effect of raising the wind-pipe, as in sing- 

 ing the higher notes, and in the act of swallowing. 



There are some muscles connected with internal organs, which 

 will be noticed in describing them, and giving a history of their 

 functions. Let us now proceed to inquire into their physiology. 



The property which muscles possess, and which distinguishes 

 them from every other tissue in the body, is their contractility. 

 This is quite different from elasticity ; it is the power of actively 

 shortening themselves. This power is constantly in action ; for 

 though we speak of the limbs being at rest, and the muscles relaxed, 

 they are never really so ; they are constantly in such a state of 

 tension as to balance their opponents, although not endeavoring to 

 overcome them. Were this not the case, time would be lost in 

 bringing the muscles into an active state when they are wanted to 

 perform any action ; but as they are constituted, they are always 

 tight, and ready to become strained the moment the stimulus of the 

 will reaches them. Their irritability is a quality somewhat different 

 from their contractility, expressing their capability of being excited 

 to exertion by certain stimulants. If in the living body, or one 

 newly dead, a muscle be pricked with a sharp instrument, it will 

 immediately contract, as has been already stated in the commence- 

 ment of this chapter. This tendency to show its contractility on 

 the application of a stimulus is its irritability. This power of 

 being excited becomes diminished by long exercise, and hence it 

 is that after fatigue we feel scarcely able to crawl, and that over- 

 driven cattle often fall down in the street ; and the capacity for 

 renewed contractions is only recovered after sufficient rest and a 

 supply of food has been taken 



There is one cause of death after which rigidity does not occur, 

 namely, the shock of electricity. The bodies of persons killed by 

 lightning never become stiff, the blood in them does not coagulate, 

 and they run very rapidly into putrefaction. This is supposed to 

 be owing to the nervous power having been exhausted by the shock, 



