54 PRINCIPLES OF -VETERINARY SCIENCE 



They may be said to clothe the skeleton more or less completely 

 except the bones of the lower limbs, which are covered only by 

 tendons and skin. 



The visceral muscles are found in the walls of the stomach, 

 intestines and other hollow organs. They are much less bulky 

 than the skeletal muscles, but are more important from the 

 standpoint of maintaining life. 



Muscular tissue is reponsible for all movements, both volun- 

 tary, such as walking and jumping, and involuntary, such as the 

 circulation of the blood through the heart and movements in all 

 the other internal organs. Since the other body tissues are 

 their servants, the muscular and nervous tissues are known as the 

 master tissues of the body. 



There are three distinct kinds of muscles, viz., (1) voluntary, 

 striped or striated, (2) involuntary, unstriped or smooth, and (3) 

 heart muscle, striped, but involuntary. 



THE VOLUNTARY MUSCLES 



These muscles are under the control of the will and by acting 

 on the bony levers enable the animal to move from place to place 

 as his brain directs. The properties of voluntary muscles are 

 assembled in the following outline: 



Location. — The voluntary muscles are located external to 

 the skeleton, so are often referred to as the skeletal muscles. 



Color. — This varies with the age of the animal and work 

 the muscles perform. In mature horses voluntary muscles are 

 dark red to brown. When exposed to the air they acquire a 

 bluish luster. The meat of a bull's carcass is darker than that 

 of a steer's or a cow's. Lean meat from a calf is lighter in color 

 than that of older bovines, as the muscles are undeveloped. 



Volume. — This varies with the location and the work per- 

 formed. Some muscles are very small in size and extremely 

 delicate, while others are large, strong, and powerful, for 

 example, those of the thigh. 



Form — The usual forms are long, short, flat, and ring-like. 

 Examples of the first are found in the limbs, of the second and 

 third between the ribs, and of the last at the natural body 

 openings. 



Shape. — The usual shapes are simple and digastric; biceps, 

 triceps, and quadriceps; penniform and semipenniform. 



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