88 



PEARL BRIGGS BULLARD 



the mouse and bat, show the lumbar region to contain the largest 

 relative amount of grey substance, while the thoracic contains 

 the smallest relative amount, in each animal. An average of the 

 ratios in the three regions is valuable since it provides a com- 

 parison of the relative amounts of white and grey substance 

 through, what we may consider, the entire cord. The average 

 of the ratios in the three regions emphasizes the well known fact 

 that, in general, the smaller the animal, the greater is the pro- 

 portion of grey substance to white. A glance at the drawings 

 of the cervical and thoracic regions of the elephant (fig. 1,0 

 and Th) and the corresponding regions of the bat (fig. 24, C and 

 Th) show the relatively high proportion of grey substance in the 

 smaller animals. 



TABLE 7 



Ratio of area of grey substance to area of white substance. Table 7 records the ratios 

 of grey substance to white substance obtained by dividing the figures in column 2 

 of table 6 into those of column 5, table 6, that is to say, the area of grey substance is 

 to the area of white substance as 1 is to the figures recorded in columns 1 , 2, and 3. 



ANIMAL 



Elephant 



Horse 



Ox 



Bear 



Hog 



Man 



Sheep 



Kangaroo 



Ape 



Dog 



Fox, 



Lynx 



Raccoon 



Rhesus monkey 



Opossum 



Cat 



Spider monkey. 

 Java monkey. . . 



Rabbit 



Agouti 



Guinea-pig 



Rat 



Mouse 



Bat 



CERVICAL 

 1 



4.8 



2.8 

 2.6 

 2.8 

 2.0 



.7 

 .3 

 .7 

 .3 

 .3 

 .3 

 .2 



2. 

 o 



1, 



2 



2. 



3. 



2. 



1.8 



1.1 



0.6 



THORACIC 



2 



12.6 

 8.3 

 6.1 

 7.9 

 7.8 

 9.5 

 7.2 

 9.8 

 9.4 

 4.3 

 8.5 

 7.7 

 8.9 

 7.2 

 5.9 

 6.2 

 5.4 

 6.9 

 4.4 

 7.3 

 2.9 

 2.3 

 1.6 

 0.3 



LUMBAR 

 3 



2.7 

 2.3 

 2.4 

 4.3 

 2.1 

 2.1 

 2.6 

 1.5 

 1.7 

 2.2 

 5 

 7 

 6 

 6 

 7 

 3 



1 

 1 

 1 

 1 

 1 

 1 

 0.9 



0.9 



AVERAGE 



4 



5.2 

 4.0 

 4.4 

 5.2 

 5.5 

 4.0 



3.6 

 3.4 

 3.4 

 2.8 

 3.3 

 2.7 

 3.9 

 2.1 

 1.8 

 1.3 

 0.6 



