THE MUSCLES. 41 



be pulled over or curved to one side by tire muscles of 

 that side overcoming those of the other. Club-foot is a 

 deformity at birth, while side curvature of the spine is very 

 often the result of sitting daily at an unsuitable desk or 

 form at school. 



The proper action of the muscle depends upon the nervous 

 supply. If the nerve branch to a muscle be injured or dis- 

 eased, its action is interfered with, and the proper balancing 

 of a certain pair of muscles lost. Squinting of the eyes may 

 be caused in this way. If the nerve on one side is divided or 

 seriously injured, the muscle is powerless, and a state of 

 paralysis exists. For instance, one side of the face may be 

 paralyzed when the muscles of the other side, having no oppo- 

 nents to act against them, draw the mouth over to that side, 

 and give a distorted appearance to the face. 



Deranged muscular action may be due to injury or disease 

 of the nerve centres. There exists a close sympathy not 

 only between the end nerves and the nerve centre, but also 

 between different and distant parts of the whole system. 

 This is seen in various affections. The irritation of a " cut- 

 ting" tooth in the infant may cause general convulsions. 

 This is reflex or transferred action. The control of the brain 

 or spinal cord may be -imperfect, and the muscles contract 

 irregularly. Instead of the measured contraction, there is 

 the spasmodic action of a group of muscles or of the whole 

 body. Sometimes the muscle contracts, and has not the 

 power to relax. If it is in the face, we have lock-jaw. This 

 is a serious and very often fatal affection, and it is sometimes 

 brought about by a very simple injury, such as the prick of a 

 pin or a fish-hook in the finger. In chorea, or St. Vitus' 

 Dance, certain muscles have ceased to be obedient to the 

 will, and persist in irregular contraction, on account of the 

 diseased condition of the nervous system ; so likewise in 

 shaking palsy. The physician meets with various forms of 



