4.24 THE NERVOUS SYSTEM. 
INTERNAL STRUCTURE OF THE SPINAL Corp. 
The spinal cord is composed of a central core of gray matter thickly coated on 
the outside by white matter. At only one spot does the gray matter come close to 
the surface, viz, at the bottom of the postero-lateral groove. 
Gray Matter of the Cord—The gray matter in the interior of the cord has 
the form of a fluted column, but it is customary to describe it as it appears in 
transverse sections through the cord. It then presents the appearance of the 
capital letter H. In each lateral half of the cord there is a semilunar or crescentic 
mass, Shaped somewhat like a comma, the concavity of which is directed outwards 
and the convexity inwards. The two crescents of opposite sides are connected 
across the middle line by a transverse band, which receives the name of the gray 
commissure (commissura grisea). The postero-median fissure cuts through the 
cord until it reaches the gray commissure. The bottom of the antero-median 
fissure, however, is separated from it by an intervening strip of white matter, which 
is termed the anterior white commissure (commissura anterior alba). In the gray 
commissure may be seen the central canal of the cord (canalis centralis), which 
tunnels the entire length of the cord and is just visible to the naked eye as a 
minute speck. The portion of the gray commissure which les behind the central 
canal is called the posterior gray commissure (commissura grisea posterior); whilst 
the portion in front receives the name of the anterior gray commissure (commissura 
erisea anterior). 
Each crescentic mass of gray matter presents certain well-defined parts. The 
projecting portions which extend behind and in front of the connecting transverse 
Column of Goll gray commissure are termed 
Column of Burdach respectively the posterior 
and the anterior cornua of 
Posterior gray matter (column 
Posterior, griseee). These stand out 
non of in marked contrast to each 
matter Other. The anterior cornu 
§ spina  (columna grisea anterior) is 
yw occessory short, thick, and very blunt 
at its extremity. Further, 
Anterior ts extremity falls consider- 
nerve-ro°F ably short of the surface of 
the cord and is separated 
Anterior column from it by a tolerably thick 
Fic. 319.—TRANSVERSE SECTION THROUGH THE Upper Parr or tHe Coating of white matter. 
CERVICAL REGION OF THE CorD. (From a specimen prepared by Through this the fascicles of 
the Weigert-Pal method, by which the white matter is rendered é com Pee de 
dark whilst the gray matter is bleached.) the anterior nerve-roots, as 
Posterior column 
Formatio reticularis 
Lateral column 
Central canal = 
Spinal accessory root Waser? 
Origin of spinal 
accessory herve 
; they emerge from the gray 
matter of the anterior horn, pass on their way to the surface. The thickened end of 
the anterior cornu is called the caput cornu, whilst the slightly constricted part close 
to the gray commissure is termed the cervix cornu. Throughout the greater part of 
the cord the posterior cornu (columna grisea posterior) is elongated and narrow, and 
is drawn out to a fine point, which almost reaches the bottom of the postero-lateral 
sulcus. This pointed extremity receives the name of the apex cornu; the slightly 
swollen part which succeeds it is the caput cornu; whilst the slightly constricted 
part adjoining the gray commissure goes under the name of the cervix cornu. 
The apex or tip of the posterior cornu differs considerably in appearance from 
the general mass of the gray matter. It is composed of a material which presents 
a lighter hue and has a somewhat translucent look. It is called the substantia 
gelatinosa Rolandi, and, when seen in transverse section, it exhibits a V-shaped out- 
line and fits on the caput cornu like a cap. 
A pointed and prominent triangular projection juts out from the external 
aspect of gray matter nearly opposite the gray commissure. This is the lateral 
horn (columna grisea lateralis), and is best marked in the upper dorsal region (Fig. 
320, B). Traced upwards it becomes absorbed in the greatly expanded anterior horn 
