1/6 Journal of Comparative Neurology. 



of substantia alba in the section is even greater than that of the 

 horse. The monkey (Arabian baboon) was appreciably larger than 

 the cat, and the dog was larger than either, yet the three give 

 sections of medulla spinalis the entire areas of which (col. 5, Table 

 III) are about the same. Notwithstanding the approximate 

 equality of the three as to the area of entire section, the mon- 

 key exceeds the dog in the area of substantia grisea in section, 

 and the cat. the smallest of the three, exeeds both the monkey 

 and the dog in this respect. The area of the entire section of 

 the elephant is 3.3 times that of man and the area of its sub- 

 stantia grisea is 3. 5 times as great as man's. In other words, 

 the area of the entire section of the elephant, in round numbers, 

 is to the area of the entire section of man as the area of the 

 substantia grisea of the elephant is to the area of substantia 

 grisea of man. Similar proportions exist between the elephant 

 and the ox, the horse, hog and dog. The proportion is de- 

 stroyed in the monkey and cat, the area of the entire section of 

 the elephant being i 5 times greater while the area ot the gray 

 substance is roughly only 8 times as great. For the remaining 

 members of the series, the relations are different in each case, 

 the relative area of the substantia grisea being greater in the 

 smaller animals. The above comparisons seem to indicate that 

 the relation between the bulk of the medulla spinalis and the 

 amount of its substantia grisea is more nearly constant for the 

 larger mammals than for the smaller. 



These relations are perhaps but another expression for 

 what is shown in columns 2 and 4 of Table IV. In column 2 

 the ratios between the area of the entire section and the area 

 of the substantia grisea contained in it are given for each speci- 

 men and thus may be compared among themselves instead of 

 each being compared with the conditions found in one individ- 

 ual, as above. It will be seen that these ratios allow the mem- 

 bers of the series to be roughly divided into three groups : For 

 the elephant, ox, horse, man, and hog, the area of the entire 

 section is approximately 6 times the area of the substantia 

 grisea contained in it ; for the dog, monkey, cat, and rabbit, it 

 is about 3 times that of the substantia grisea, and for the rat, 



