Hardestv, Medulla Spinalis of the Elephant. 165 



area of entire section and a smaller area of substantia grisea in 

 it. The areas of sections for the dog, monkey and cat are ap- 

 proximately the same, but the area of the substantia grisea in 

 the sections is least for the largest of the three and greatest for 

 the smallest. A glance at column 7 will show that the cat 

 acquires its greatest area tiirough the size of its columnae pos- 

 teriores (substantia gelatinosa) and that, in reality, the monkey 

 possesses the largest columnae anteriores and, as would follow, 

 the greatest number of motor axones arising at this level. The 

 elephant has an area of section 3 times as great as man and also 

 an area of substantia grisea in the section 3 times great, while 

 for the mouse, the area of the section from the elephant is 154 

 times that of the mouse, but the area of the contained substan- 

 tia is only 54 times that of the mouse. 



In column i of Table III are recorded the sizes of the 

 cell-bodies situated in the columnae anteriores of the largest 

 cervical segment of the different animals of the series. The 

 size is expressed in terms of the average mean diameter of the 

 ten largest cell bodies found in three adjacent sections, one of 

 which being the section employed in obtaining the data given 

 in the remaining columns of the Table. The measurements were 

 made with an ocular micrometer and under a magnihcation of 

 712 diameters (Zeiss). In each case the two diameters measured 

 were the longest diameter of the cell-body and the diameter at 

 right angles to this. All diameters taken passed through the 

 center involving the nucleus. When a measurement invt^ived 

 one of the larger dendrites, the diameter had to be judged by 

 an approximate estimation of what the diameter \\ ould be were 

 the section of the cell body a circular disc with the more visi- 

 ble portion of the dendrite included in it. A special effort was 

 made to employ similar judgments in all cases. In order to 

 avoid measuring the same cell body in two sections, and to 

 assure the measurements passing approximately through the 

 center, only such cell-bodies were measured as contained nu- 

 cleoli. The method of measurements may be seen in Plate 

 XIII where the shape and relative size is represented by one of 

 the ten cell bodies measured from each of the specimens. The 



