THE SPINAL CORD 651 



dorsal column or horn is elongatod 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 

 (Rolandi). The ventral column or horn is short, thick and rounded, and is sepa- 

 rated from the surface of the cord by a thick layer of white matter, through which 

 the filjcrs of the ventral roots of the spinal nerves pass. From the middle of the 

 cervical region to the lumbar region there is a medial ]:)rojection of gray matter on 

 the lower part of the dorsal column: this is the nucleus dorsalis or Clarke's column. 

 In the anterior part of the cord there is an outward i:)rojection of the gray matter at 

 the base of the ventral horn; this is termed the lateral column or horn. The 

 demarcation between the graj' 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 IS mm. 

 and its greatest thickness aljout S mm. It has dorsally a deep median sulcus and a distinct 

 dorso-lateral sulcus. Lateral grooves are also present. The dorsal cornua are strongly e\'ert('d. 

 Each has an expanded head, which comes very close to the surface of the cord, and has an 

 extensive cap of sul^stantia 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 al^out 2.5 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 ventral surface. Each l>ears a prominence on its inner side near the l)ase. The gray 

 commissure is considerably above tlie 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 10 mm. 

 The gray columns are close together, the gray commissure being only about 1 mm. in length, 

 and lying considerably al)ove the middle of the section. The dorsal cornua are short and have 

 slightly enlarged ends. The ventral cornua have a uniform diameter, turn very little outward, 

 antl end about 3 mm. from the ventral surface. (3) The luml)ar enlargement is much flattened, 

 especially dorsally. The transverse diameter is al)Out 22 mm. and the dorso-ventral 9 to 10 mm. 

 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 ancl 

 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 out- 

 ward. (4) In the first sacral verteljra 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 intermediate mass. 



The ventral horn contains large cells, the axones of which emerge as the fibers of the ventral 

 nerve-roots (Fila radiculariaj. The axones of many cells cross to the opposite side in the white 

 commissure and pa.ss 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 pa.ss 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 cerebellum. 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 

 ventral columns (Funiculi ventrales) are situated on either side between the median 

 fissure and the ventral gray columns. They are connected above the fissure by 

 the white commissure. The lateral columns (Funiculi laterales) lie external to the 

 gray columns on either side; their limits are indicated superficially by the dorso- 

 lateral groove and the emergence of the ventral root-fibers. The paramedian 



