THE ANATOMY OF THE HORSE 45 



will absorb the most oxygen into the body and cast off the 

 most impurities into the atmosphere. Thus the combina- 

 tion of strong heart and capacious lungs is most important. 



The nervous system of the horse is centered in the brain 

 and spinal cord, from which it radiates throughout the 

 entire body. The spinal cord is from 76 to 78 inches long 

 and weighs eight and one-half to nine ounces, and is nearly 

 cylindrical. The brain weighs about 23 ounces, and is 

 divided into three parts, the medula oblongata, the cere- 

 brum and cerebellum. . The cerebrum is located just below 

 the forehead and is the organ of thought or intelligence. 

 The cerebellum is a very small part of the brain, directly 

 back of the cerebrum, and as expressed by Hayes, "is the 

 organ of muscular sense. ' ' The medulla oblongata is simply 

 the connecting link between the brain proper and the spinal 

 cord. The entire nervous system is made up of certain 

 tissues that have the property of extreme irritability or 

 sensitiveness, especially as applied to external conditions. 

 It is the property of this system to act between these ex- 

 ternal influences and the inner ones of the body tissues. 

 Thus the nerves convey to the muscles and other organs 

 motor influences whereby movement of the animal body 

 takes place through contraction of the rauscular tissues. 

 The amount of contraction which may take place will be 

 in proportion to the amount of stimulation of the nerves. 

 With some animals the nervous system is more sensitive 

 than with others, even though apparently much alike 

 otherwise. Light horses, such as Thoroughbreds, are very 

 generally regarded as more nervous than the heavy draft, 

 and respond more actively to muscular stimulation. 



The temperament of the horse relates to his nervous 

 and mental character, and may be regarded as of much 

 importance, bearing on his usefulness to man. When natu- 

 rally active and quick to move and think, the horse is said 

 to have a nervous temperament. The light weight horse 

 of the racing class possesses this temperament. When 

 characteristically slow to move or act, the horse is said to 



