Dunn, Inncri'ation of the Thigh in the Frog. 235 



accurate millimeter scale. The vertical of the two measure- 

 ments for each lateral surface was then computed. The length 

 of each of these surfaces was the same as the corresponding 

 lateral line of the outline of the thigh. Having thus ascertained 

 the lengths and the mean width, the areas of the lateral surfaces 

 were easily computed. In the total area given in Table VIII 

 the decimal parts of a millimeter are disregarded. 



TABLE VIII. 

 Relation of cutaneous fibers to the areas supplied. 



Rana vis. D 



Left leg 

 Thigh 



Lutaneous area 

 sq. mm. 



1374 



Number of fibers. 



Sq. mm. to each 

 fiber. 



frog B I frog C 

 871 1219 



frog B I frog C 

 1.58 1.13 



The total cutaneous surface of the left thigh in frog D was 

 found to be 1374 square millimeters. If this area was inner- 

 vated by the 87 1 cutaneous thigh fibers of frog B, the average 

 area to each fiber would be 1.58 square miUimeters. If sup- 

 plied by the 12 19 cutaneous thigh fibers of frog C, the cutane- 

 ous surface to each fiber would be 1.13 square millimeters, or 

 in short the cutaneous surface receiving its innervation from each 

 fiber would be from i.i to 1.5 sq. mm., if the fibers were evenly 

 distributed to the surface. 



C. Size of the Fibets. 



As the determination of the size of the nerve fibers is for 

 the purpose of comparison, the area /<7r each fiber, obtained by 

 dividing the area of the section by the number of nerve fibers 

 at that level, is substituted for the area actually occupied by 

 each fiber. 



The computation of the area for each section was accom- 

 plished with great care. Whenever the fibers showed lines of 

 separation, the area of each division was computed separately 

 rather than to include an unoccupied area which would increase 

 the average area for each fiber. Whatever spreading was un- 

 avoidable in handling such extremely thin sections was uniform 



