HEAD AND NECK OF THE HORSE 



169 



gelatinosa (Roland i), so called from its semitransparent character. 

 Occasionally a slight constriction, or neck (cervix columnse dorsalis), 

 marks off" the dorsal column from the rest of the grey matter. 



In some regions of the cord a projection — the lateral column 

 (columna lateralis) — maybe observed opposite the grey commissures; 

 and it is often difficult to clearly define the boundary of the grey 

 matter in the concavity formed by the dorsal and ventral columns, 

 owing to an admixture of grey and white matter known as the 

 formatio reticularis. 



The grey columns are largest in the cervical and sacral regions, 

 and particularly so on a level with the origin of those nerves that form 

 the limb-plexuses ; while they are smallest in the thoracic and early 

 lumbar regions. 



L.I. s.i. 



Fig. 78. — Transverse sections of the spinal cord at different levels. 



The white matter of the cord is disposed external to the grey 

 columns, and consequently is divided into the three funiculi previously 

 mentioned. A dorsal funiculus^ (funiculus dorsalis), triangular in 

 section, lies between the dorsal grey column and the dorsal median 

 septum. A lateral funiculus (funiculus lateralis) occupies the con- 

 cavity lateral to the grey columns. A ventral funiculus (funiculus 

 ventralis) fills the interval between the grey column and the ventral 

 median fissure. The two ventral funiculi are connected across the bottom 

 of the fissure by the ivhite commissure (commissura ventralis alba). 

 From the circumstance that the ventral grey column does not reach the 

 surface of the cord, it is obvious that the lateral and ventral funiculi 

 are only imperfectly separated. For this reason they are sometimes 

 taken together as the ventro-lateral funiculus. As previously stated, in 

 1 Funiculus (dim. of funis) [L.], a little cord. 



