DISSECTION OF THE DOG 205 



intermediate groove (sulcus intermedius dorsalis) divides the dorsal funiculus 

 into a medial fasciculus gracilis of Goll and a lateral fasciculus cuneatus of 

 Burdach. Goll's fasciculus is much the narrower. 



In the cervical and thoracic regions, moreover, a longitudinal groove runs 

 along the side of the spinal cord midway between the dorsal and ventral 

 lateral grooves. 



Sectiones medulla spinalis.— Sections should be made across the cord 

 in different regions and the cut surfaces studied. The bilateral nature of 

 the cord is obvious. The ventral median fissure cuts into it to a considerable 

 depth, and a median septum (septum medianum dorsale) continues the dorsal 

 median groove into the interior. Each half contains grey and white matter ; 

 the former more deeply placed and in the form of a curved or comma-shaped 

 mass. The grey matter is continued from one side of the cord to the other 

 by the dorsal and ventral grey commissures (commissura dorsaUs grisea et 

 eommissura ventrahs grisea), between which is the central canal of the cord 

 (canalis centralis) surrounded by the central grey matter. 



The exact shape of the sectional area of the grey matter varies considerably 

 in different regions, but in the main it may be indicated by saying that it 

 resembles the capital letter H ; the cross-bar of the letter being represented 

 by the grey commissures. Each half of the cord contains a dorsal and ventral 

 column of grey matter (columna dorsalis et columna ventrahs). Of these the 

 ventral is the larger, and terminates bluntly some distance from the surface. 

 The dorsal column approaches the surface very nearly, and terminates in a 

 pointed apex. 



Occasionally a shght constriction, the nech of the dorsal column (cervix 

 columnae dorsalis), marks off this column from the rest of the grey matter. 

 The apex of the dorsal column is covered by a particular kind of grey matter 

 called the gelatinous substance of Rolando (substantia gelatinosa [Rolandi]) 

 from its semi-transparent character. 



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

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

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

 regions. 



The white matter is disposed external to the grey columns, and consequently 

 is divided into three funiculi. 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 concavity lateral to the 

 grey columns. A ventral funiculus (funiculus ventrahs) fills the interval be- 

 tween the ventral grey column and the ventral median fissure. The two 

 ventral funicuh are connected across the bottom of the fissure by the white 

 commissure (commissura ventrahs alba). From the circumstance that the 

 ventral grey column does not reach the surface, it is obvious that the lateral 

 and ventral white funicuh are only imperfectly separated. 



