1905.] 



Cord of the Macaque Monkey. 



105 



The rise and fall in percentage of grey and white substance respectively 

 is most rapid between the upper portion of the first lumbar region and the 

 lower portion of the fifth lumbar region. Within these limits the rise and. 

 fall is most marked in the fourth and fifth lumbar regions, more particularly 

 in the fifth. Through the first, second, and the greater part of the third 

 sacral regions, there is very little variation in the percentage values. 



In the middle portion of the fourth sacral region the percentage of grey 

 and white substance is equal, and through the first, second, and part of the 

 third coccygeal region the percentage of grey substance is higher than that of 

 white. 



The maximum percentage of grey substance and the lowest percentage of 

 white substance is found in the first coccygeal region (ca. 53 per cent, and 

 47 per cent, respectively). The maximum percentage of white and the 

 lowest percentage of grey substance is found in the first lumbar region 

 (ca. 80 per cent, and 20 per cent, respectively). 



(a) Percentage of the Dorsal Columns (P) (Chart IV, Table VII). 



The percentage of the dorsal columns (P) to the cross-section of the cord 

 falls from the first lumbar region to the end of the cord. 



The dorsal columns constitute 22 per cent, of the cross-section of the 

 cord in the first lumbar region, their percentage value being, approxi- 

 mately, the same in this as in both the sixth and twelfth dorsal (thoracic) 

 regions (see Table VII). 



Through the first lumbar region the percentage value of the dorsal 

 columns is higher than that of the grey substance ; while it is lower than 

 this from the second lumbar region to the end of the cord. 



Between the upper portion of the first lumbar region and the lower portion 

 of the third coccygeal region there is a total fall of 14 in the percentage of 

 the dorsal columns. The fall is most rapid between the upper portion of the 

 first lumbar and that of the sixth lumbar region. It occurs chiefly in the 

 third, fourth, and fifth, and more particularly in the fourth lumbar. From 

 the sixth lumbar region to the end of the cord the fall is very gradual, 

 the percentage value being approximately the same through the sacral 

 regions. 



(b) Percentage of the Ventro-lateral Columns (A) (Chart IV, Table VII). 



The percentage of the ventro-lateral columns (A) to the cross-section of 

 the cord falls fromca. 57 per cent, in the first lumbar region toco.. 36 percent, 

 in the first coccygeal, and rises from the middle portion of the latter region to 

 43 per cent, in the third coccygeal. 



