32 THE HOESE IN HEALTH AND DISEASE 



(5) Urogenital system, or organs of urination and reproduction. 



(6) Circulatory system, or organs of circulation. 



(7) Nervous system, or organs of innervation. 

 Descriptive terms are employed to indicate the exact position 



and direction of parts and organs of the body. These terms 

 refer to the horse in the ordinary standing position and must be 

 learned. The surface directed toward the ground is termed 

 inferior or ventral, and the opposite surface is superior or dorsal. 

 An imaginary median plane divides the body into halves. A struc- 

 ture or surface which is nearer than another to the median plane is 

 internal to it; and an object or surface which is further than another 

 from the median plane is external or lateral to it. The head end 

 of the body is termed anterior, cephalic, or cranial; and the tail 

 end, posterior or caudal. Proximal and distal represent distances 

 from the vertebral column. 



