Hardesty, Medulla Spinalis of tJic Elephaiti. 171 



passing from the medulla spinalis to the fore foot of the ele- 

 phant would have a length at least 7 feet' or 2128 mm. Assum- 

 ing that the larger cell-bodies give origin to the larger axones 

 (Donaldson ('98) ) and that some of the larger axones extend to 

 the fore foot, measurements were made of the diameter exclusive 

 of the medullary sheath of a number of the larger axones of the 

 radix anterior of the elephant which were cut transversel)' and 

 mounted in company with the sections containing the cell bodies 

 measured. These axones were suited to the purpose not only be- 

 cause they belonged to the radix anterior of the same segnitnt as 

 the cell-bodies concerned, but because they had been subjected to 

 the identical conditions in dehydration, embedding, etc. applied 

 to the cell-bodies The average diameter of these axones (axial 

 spaces within sheath) proved to be 11.76 micra. This gives 

 the section of the axone an area of 108.55 sq. micra. Consid- 

 ering the axone as a cylinder having this as the area of its base 

 and an altitude of 7 feet, such a cylinder has a volume of 230,- 

 994,400 cu. micra. Then if the cell body be considered as a 

 sphere with a diameter of 84.4 micra, such a sphere has a vol- 

 ume of 314,634 cu. micra. In other words the axone arising 

 in the inlumescentia cervicalis of the elephant may have a vol- 

 ume 734 times the volume of the cell body giving origin to it. 

 And the volume of the entire neurone, exclusive of collateral 

 branches and the greater portion of the dendritic processes, 

 maybe 23 1,309,034 cu. micra. 



For man the average caliber of the axone (axial space) of 

 the radix anterior cut transversely in company with the sections 

 containing the cell bodies measured, was 8.4 micra. Tins gives 

 the section of the axone an area o( 55.4 sq. micra. 800 mm, 

 is considered a conservative estimate of the average length 

 between the intumescentia cervicalis of man and the muscles 



' An elephant of 8,000 pounds has a height of fully S feet from sole 

 of foot to top of back between shoulders. Twelve inches of this is allowed 

 for the thickness of the tissue overlying the medulla spinalis. This height for 

 "Bolivar" is about 10 feet and records obtained through the kindness of Ward's 

 Natural History establishment show that the corresponding height of "Jumbo" 

 was 12 feet. Jumbo's greateit height was produced by an extraordinary arch 

 in the back. 



