90 THE STRUCTURE OF THE FOWL 



The spinal cord is a bilaterally symmetrical 

 column of nerve-matter extending through 

 the greater part of the vertebral column from 

 the foramen magnum of the occipital bone 

 where it is continuous with the brain. The 

 diameter of the cord is not uniform inasmuch 

 as there are swollen sections with which the 

 nerves of the limbs are connected, and its 

 caudal extremity in the sacrum is tapering 

 and finely thread-like. On the dorsal surface 

 of the enlargement (lumbar) from which the 

 nerves of the leg arise, the two halves of the 

 cord separate to enclose an elliptical sinus in 

 which is contained a gelatinous substance. 



A transverse section shows that the cord 

 consists of two symmetrical halves, and reveals 

 the presence of a minute central canal traversing 

 its whole length. The section also demon- 

 strates that two kinds of nerve-tissue enter into 

 its formation. White nerve-matter, composed 

 essentially of nerve-fibres, forms an outer 

 covering to grey matter within. The grey 

 matter is arranged in the form (in transverse 

 sections) of two masses, shaped something 

 like a comma, one in each half of the cord, 

 placed back to back and connected by a 

 transverse ' grey band embracing the central |j 



