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THE SPINAL CORD 767 
a capital H, the cross-bar of the letter being formed by the gray commissure. 
Each lateral part is considered as consisting of dorsal and ventral gray columns 
(Columna grisea dorsalis, ventralis), which appear in cross-section as the so-called 
horns (Cornu dorsale, ventrale). In the greater part of the cord the dorsal column 
or horn is elongated and narrow and tapers to a point which extends almost to the 
surface of the cord at the attachment of the dorsal root-fibers of the spinal nerves. 
Its apex or tip consists of gray matter which is lighter in color and less opaque 
than that of the rest of the horn, and is termed the substantia gelatinosa. The 
ventral column or horn is short, thick, and rounded, and is separated from the surface 
of the cord by a thick layer of white matter, through which the fibers of the ventral 
roots of the spinal nerves pass. From the middle of the cervical region to the 
lumbar region there is a medial projection of gray matter on the ventral part of the 
dorsal column; this is the nucleus dorsalis.!_ In the anterior part of the cord there 
is an outward projection of the gray matter at the base of the ventral horn; this 
is termed the lateral column or horn. The demarcation between the gray and 
white matter is in many places indistinct; this is especially the case laterally, 
where processes of gray matter extend into the white substance, producing what 
is known as the formatio reticularis. 
Cross-sections of the spinal cord present the following gross regional characters: (1) The 
cervical cord near the medulla is compressed dorso-ventrally. Its width is about 18 mm. and 
its greatest thickness about 8 mm. It has dorsally a deep median sulcus and a distinet dorso- 
lateral sulcus. Lateral grooves are also present. The dorsal cornua are strongly everted. Each 
has an expanded head, which comes very close to the surface of the cord, and has an extensive 
cap of substantia gelatinosa. The neck is distinct. The ventral cornua are short and blunt and 
diverge very little. The gray commissure is about in the middle of the section, and 2.5 mm. 
in length. According to Dexler, the column between the median and lateral grooves dorsally 
is the funiculus cuneatus, the funiculus gracilis being very small and not showing on the surface 
in this region. In the middle of the cervical region the diameters are about 16 mm. and 10 mm. 
respectively. The ventral surface is somewhat flattened. The dorsal cornua have pointed ends 
and turn decidedly outward. The ventral cornua are short and thick and are directed very slightly 
outward; their ends are about 4 mm. from the ventral surface. The gray commissure is just 
above the middle of the section and is about 2 mm. long. The cervical enlargement measures 
about 25 mm. transversely and 12 mm. vertically. The dorsal cornua are smaller than the ventral 
and have a large cap of substantia gelatinosa. The ventral cornua are short and thick, curve 
strongly outward, and are about 4 mm. from the v entral surfa¢e. Each bears a prominence on its 
medial side near the base. The gray commissure is considerably above the middle of the section 
and is about 4 mm. long. (2) In the middle of the thoracic region the cross-section is biconvex, 
the ventral surface being the more strongly curved. The transverse diameter is about 15 mm. 
and the dorso-ventral about 10mm. The gray columns are close together, the gray commissure 
being only about 1 mm. in length, and lying considerably above the middle of the section. The 
dorsal cornua are short and have slightly enlarged ends. The ventral cornua have a uniform diame- 
ter, turn very little outward, and end about 3 mm. from the ventral surface. (3) The lumbar enlarge- 
ment is much flattened, especially dorsally. The transverse diameter is about 22 mm. and the 
dorso-ventral9to10mm. The cornua are very large. The ventral cornua are thick and rounded 
and turn sharply outward; they end about 2 mm. from the ventral surface. The dorsal cornua 
are smaller and shorter and do not diverge so strongly. The gray commissure is about in the 
middle of the section and is about 3 mm. long. In the third lumbar vertebra the cord is about 
3 mm. narrower and thicker, and both surfaces are about equally convex. The dorsal cornua are 
smaller, considerably everted, and constricted in the middle. The ventral cornua are very short 
and do not turn outward. (4) In the first sacral vertebra the cord is almost round and is 5 to 6 mm. 
in diameter; the cornua are relatively very large and the commissure has the form of a high inter- 
mediate mass. 
The ventral horn contains large cells, the axones of which emerge as the fibers of the ventral 
nerve-roots (Fila radicularia). The axones of many cells cross to the opposite side in the white 
commissure and pass out in a ventral root of that side, or enter the white matter and pass forward 
and backward, associating various segments of the cord. Some pass to the ventral horn of the 
opposite side at the same or at different levels. Others pass to the periphery of the cord, join 
the cerebellospinal fasciculus, and extend to the earebellin. Scattered through the gray matter 
are many smaller cells with axones which pursue a short course and serve to connect different 
parts of the gray matter. 
The white matter of the spinal cord is divided into three pairs of columns. 
The dorsal columns (Funiculi dorsales) lie on either side of the dorsal median septum 
and extend outward to the dorso-lateral groove and the dorsal gray column. The 
1 Also known as Clarke’s column. 
