1905.] 



Cord of the Macaque Monkey. 



101 



to the end of the cord. The' decrease is most marked between the fifth 

 lumbar and the first sacral regions, and becomes very gradual in the lower 

 sacral and in the coccygeal regions. 



In the first lumbar region the section area of the dorsal columns (P) is 

 greater than that of the grey substance (G). This is also the case in both the 

 sixth and twelfth dorsal (thoracic) regions (see Tables II and IV). In the 

 second lumbar region, and throughout the remainder of the cord below 

 this, the section area of the dorsal columns is less than that of the grey 

 substance. 



It is of interest to note that the section area of the dorsal columns in the 

 greater part of the sixth lumbar region is approximately the same as that 

 in the sixth dorsal (thoracic). 



The section area of the ventro-lateral columns (A) (Chart II, Table V) 

 remains about the same through the first and the greater part of the second 

 lumbar region (ca. 7*2 sq. mm.). It is somewhat larger in the third, and 

 increases rapidly from the lower portion of this and throughout the fourth 

 lumbar region. 



The maximum (9"25 sq. mm.) is reached in the lower portion of the fourth 

 lumbar, and thus occurs in the same region as the maximum section areas of 

 the cord, white substance, and dorsal columns. 



The chief development of the ventro-lateral columns extends from the third 

 lumbar (lower) to the lower portion of the fifth lumbar region, the section 

 area in the upper portion of the fifth being nearly the same as that in the 

 lower portion of the fourth. 



The section area diminishes from the fourth lumbar region (lower part) to 

 the end of the cord. The decrease is rapid to the third sacral region, and is 

 most marked in the fifth, sixth, and seventh lumbar regions. 



From the first to the fifth lumbar region inclusive, the section area of the 

 ventro-lateral columns (A) exceeds that of the grey substance (G), especially 

 in the first three lumbar regions. The section areas are approximately equal 

 in the sixth lumbar region. From the seventh lumbar region to the end of 

 the cord the section area of the ventro-lateral columns is less than that of 

 the grey substance, but the areas approach each other very nearly in the lower 

 coccygeal regions. 



The increase in the section area of the whole white substance (Chart I, W) 

 between the first and the fourth lumbar, and the decrease between the fourth 

 and the sixth lumbar regions, is chiefly due to the variation in the ventro- 

 lateral columns (Chart II, A). The actual increase and decrease in the 

 section area of these columns (A) being about twice as great as that of the 

 dorsal columns (P). 



