ANATOMY OF THE NERVOUS SYSTEM 123 



half of the gray matter is crescent-shaped, and the crescents are 

 turned back to back and united across the middle line by the 

 gray commissure. The tips of each crescent are called its horns or 

 cornua, and the ventral horn on each side is thicker and larger 

 than the dorsal. In the cervical and lumbar enlargements the 

 proportion of white to gray matter is greater than elsewhere ; and 

 as the cord approaches the medulla oblongata its central gray 

 mass becomes irregular in form and begins to break up into 

 smaller portions. If lines be drawn on the transverse section of 

 the cord from the tip of each horn of the gray matter to the 

 nearest point of the surface, the white substance in each half will 

 be divided into three portions: one between the ventral fissure 

 and the ventral cornu, and called the ventral white column; one 



Fio. 60. Diagram illustrating the general relationships of the parts of the brain. 



A, fore-brain; b, midbrain; B, cerebellum; C { pons Varolii; D, medulla oblongata; 



B, C, and D together constitute the hind-brain. 



between the dorsal fissure and the dorsal cornu, and called the 

 dorsal white column; while the remaining one lying in the hollow 

 of the crescent and between the two horns is the lateral column: 

 the ventral and lateral columns of the same side are frequently 

 named the ventrolatcral column. A certain amount of white 

 substance crosses the middle line at the bottom of the ventral 

 fissure; this forms the ventral white commissure. There is no 

 dorsal white commissure, the bottom of the dorsal fissure being 



