The Nervous System. 105 



diabetic centers are located in this division of the brain. 

 Injury to the medulla generally results in instantaneous 

 death, breathing being at once stopped. 



The spinal cord is located in the spinal canal, a hollow, 

 bony cavity running throngh the vertebrae,- this canal is 

 of far greater size than the cord, thus allowing room for 

 extreme movements, such as bending the head around to 

 the side. The spinal cord might be considered as an 

 immense telegraph cable, made up of a number of small 

 cables or wires, each carrying its own message. Some 

 of the fibres (tracts) cross at the upper part of the cord, 

 and for this reason an injury on one side of the brain 

 will show paralysis on the opposite side of the body. 

 The cord is also of interest because it contains the fol- 

 lowing nerve centers: the ano- spinal, in the region of the 

 loins, controls the passage of feces ; the vesico- spinal, in 

 the same locality, governs the passage of urine; the 

 centers governing the sexual organs are also located in 

 the region of the loins; centers controlling the blood ves- 

 sels (vaso- motor centers) and nutrition of tissues (trophic 

 centers) are found throughout the cord. An unfortu- 

 nate result of nerving horses sometimes is seen in the 

 sloughing of the entire foot; such illustrates the control 

 of the nutrition of a part by nerves as well as the prop- 

 erty of sensation given by them to a part. Injury to the 

 upper part of the spine shows in paralysis of the lower 

 part of the body, and the continual passage of urine and 

 feces, or else complete stoppage of these functions. In 

 addition to the above functions, the spinal cord gives off 

 pairs of spinal nerves, at such points it is enlarged cor- 

 responding to the number given off, which leave by two 



