STRUCTURE OF THE HORSE. 131 



movements of the iitenis and erectile tissue are situated in the 

 lumbar region of the cord. All along the spinal cord, from its 

 origin to the tail, other nerves are given off at certain intervals. 

 The spinal cord is composed of six distinct rods running through 

 its whole length, three on each side, and the fibers of the two 

 columns proceed to their destinations, enveloped in the same 

 sheath and apparently as one nerve. They are united, yet dis- 

 tinct, apparently constituting one nerve, yet neither their sub- 

 stance nor their office is confounded. The cerebrum seems to 

 be the seat of intelligence and will; the cerebellum seems to 

 combine and balance the several muscular actions of the body; 

 the medulla oblongata superintends respiration, mastication, and 

 deglutition. Besides these are the ganglia, which are intended 

 to subserve what are called the reflex actions of the organs of 

 locomotion, etc., occupying the whole length of the spinal cord, 

 one on each side. There are also the sympathetic systems of 

 ganglia, which especially control the vital organs of circulation, 

 digestion, and excretion. 



THE MALE REPRODUCTIVE ORGANS. 



These consist of two testicles or seminal glands, with their 

 excretory tubes, a musculo-glandular organ, the prostate, which 

 provides a material for. the dilution of the semen, and by its 

 sphincteric contraction aids in the ejaculation of the spermatic 

 fluid, at the same time intercepting its retrograde passage into 

 the bladder; an organ of copulation, the penis, and a canal, the 

 urethra, which pierces the prostate and penis, and serves as the 

 transit for both the generative and urinary secretions. The 

 testicles are two in numl)er, and lie in a common pouch of in- 

 tegument, called the scrotum. In fetal life they are at first 

 situated in the abdominal cavity behind the kidneys. At a cer- 

 tain period they descend through the vaginal canal into the 

 scrotum. They are glandular organs which secrete the semen. 

 Lying upon the posterior border of each testicle is_ a narrow- 

 flattened body, termed the epididymis. The testicles are sus- 



