PRINCIPAL REGIONS OF SPINAL CORD 



75 



the data in tables 2, 3, and 4 and is described in the discussion 

 of it. Table 6 records the exact areas of the several components 

 of the cord as obtained by tracings of the drawings with the 

 Amsler planimeter. Separate readings were taken for the area 

 of the grey figure, the area of the dorsal funiculus, and the total 

 area. Other measurements were obtained by computing differ- 

 ences. Each tracing with the planimeter was taken three times 

 and the average computed to minimize mechanical errors. The 



Text figure A. Outline of a section of the spinal cord with lines, numbered, 

 indicating the extent and direction of each of the measurements taken of the 

 different sections of the various spinal cords dealt with. These measurements 

 are recorded in tables 2, 3, and 4. The numbers of the lines correspond to like 

 numbers in the columns of the tables: 1, dorso-ventral diameter; 2, lateral diam- 

 eter; 4, thickness of grey figure; 5, width of grey figure; 7, width of ventral horn; 

 8, width of dorsal horn; 9, width of grey commissure. 



average of the three readings, which were in terms of square 

 centimeters and fractions of square centimeters including vernier 

 readings, were reduced by sixty-four, the square of the magnifi- 

 cation. The actual areas of the specimens thus obtained are 

 here recorded in terms of square millimeters. For the sake of 

 convenience, I have selected certai^i data from table 6 and com- 

 piled the tables of ratios, 7, 8a, and 8b. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 14, NO. 1 



