462 A MANUAL OF VETERINARY PHYSIOLOGY 



not reach down to the centre, while the dorsal median fissure is 

 narrow and deep. Each half of the cord is seen to consist of 

 dorsal, lateral, and ventral columns, separated from each other by 

 a shallow longitudinal groove. A section of the cord shows it 

 to be made up of both white and grey matter, the latter, internally 

 placed, forming the medulla. This is arranged something like 

 the letter H, or like two inverted commas placed back to back. 

 The shape of the grey matter on transverse section depends 

 entirely on the region of the cord examined. This may be seen 



Fig. 137.— Transverse Section of the Spinal Cord in the Cervical Region 

 X 8d. The Lines in the Lateral and Superior Columns running from 

 the Outer Margin are Laminae of the Pia Mater (M'Kendrick). 



a, Processus reticularis ; b, dorsal horn ; c, grey commissure ; d, dorsal septum ; 

 e, Goll's column ;/, superior column ; g, point of entry of dorsal root ; k, sub- 

 stantia gelatinosa ; i, lateral column ; ;', large multipolar nerve -cells ; k, ventral 

 horn ; /, white commissure ; m, inferior longitudinal fissure ; n, inferior 

 column ; 0, central canal ; p, point of exit of ventral roots. 



in Fig. 136, which shows three sections of the cord. The dorsal 

 and ventral ends of the comma, or crescent-shaped halves of the 

 grey matter, are spoken of as the cornua. From the dorsal 

 cornu the afferent or sensory fibres run ; from the ventral run the 

 efferent or motor roots. The white substance of the cord also 

 varies in thickness (see Fig. 136). Stated generally, the cord 

 increases in white matter from the tail to the head. The grey 

 matter is largest in the cervical and lumbo-sacral enlargements, 

 and this increase and decrease in size corresponds with the in- 



