404 Types and Market Classes of Live Stock 



tubes, and lungs. The heart is large and four chambered, and the 

 blood vessels are large and have strong, thick walls. Thus is the horse 

 well fitted for his athletic life. 



Nervous system. — The nervous system of the horse is well develop- 

 ed and comprises the brain, spinal cord, and branching nerves. The 

 horse differs from a mere machine in that he is largely capable of guid- 

 ing his own movements without aid from his driver. Training ac- 

 complishes much in this regard, but the less a horse is possessed of 

 intelligence and nervous control, the less he is automatic as a motor, 

 and the more he becomes dependent upon his driver. 



Integumentary system. — The hair or coat is shed in the spring 

 and autumn, except that of the mane and tail which is permanent. 

 There are both sweat glands and sebaceous glands in the skin, but the 

 former are practically absent from the limbs. 



\- 



\ 



Fig. 147. — Bones of the fore leg. 1, Scapula; 2, humerus; 3, radius and ulna; 

 4, seven or eight carpal bones; 5, cannon bone and two splint bones; 6, two sesamoid 

 bones; 7, large pastern bone; 8, small pastern bone; 9, navicular bone; 10, coffin bone. 



Anatomy of the Fore Leg 



From the top downward, the bones of the fore leg are as indicated 

 in the accompanying diagram. The fore leg is composed of a scapula 

 (or shoulder blade) which is articulated to the humerus (or arm) by 

 a ball-and-socket joint, and the arm in turn articulates with the radius 

 by a hinge joint. The lower end of the radius rests upon the upper 

 row of the carpal bones of which there are 7 or 8 in the horse, corre- 

 sponding to the wrist in man. Below the carpus (knee) is the large 

 metacarpal (or cannon) bone, and articulated with the back of it are 

 two slender rods of bones — the small metacarpal (or splint) bones. 

 The lower end of the large cannon bone forms a hinge with the first 



