42 PHYSIOLOGY AND TEMPERANCE. 



disease due to a want of harmonious action between the 

 muscular and nervous systems. 



4. Classification of Muscles. A very large number of 

 the muscles of the body are wholly under the control of 

 the will. These are called voluntary. A certain number act 

 independently of the will. These are called involuntary. As 

 instances of each class, the muscles of the extremities are 

 voluntary, while those which send the food along the aliment- 

 ary canal are involuntary. Certain muscles partake of the 

 character of each kind, as the respiratory. One may hold his 

 breath for a time by a voluntary act, but breathing proceeds 

 without any effort of the will, particularly during sleep. 

 Although we have no will-power over the involuntary mus- 

 cles, yet they are under the control of the nervous system. 



The voluntary muscles are also known as striped. They 

 are so named from their appearance under the microscope, as 

 already pointed out. The involuntary are unstriped, being 

 made up of slender spindle-shaped cells, which do not appear 

 striped under the microscope. They are not attached to bone. 

 These muscles are made to act by some stimulus. Food, for 

 instance, the taking of which into the mouth and chewing 

 is voluntary, when it passes a certain point is beyond the 

 v.ontrol of the will. It acts as a stimulus to the involuntary 

 muscles of the gullet, and is passed along to the stomach by a 

 worm-like motion. 



5. The Levers of the Body. Special reference to a few 

 of the voluntary muscles will show the principle upon which 

 they cause movement of a limb. The movement is accom- 

 plished by leverage. There is a weight to be moved, a, fulcrum 

 for the lever, and the application of the power. The limb or 

 bone is the weight, the joint is the fulcrum, the power is in 

 the muscle. 



The lever of the first kind, where the fulcrum is between 

 the weight and the power, is not common, but is seen in the 



