172 'Journal of Comparative Neurology and Psychology. 



compacting of the fibers, than to a diminution in their individual 

 diameters, and it is therefore not thought that the normal diameters 

 of the fibers are as much modified as the above measurements 

 would indicate. 



The samples of nerve were teased with fine needles under a dis- 

 secting microscope, and measured directly with a compound micro- 

 scope, using lenses and eyepieces (with micrometer scales), suited 

 to the determination of length on the one hand and diameter on 

 the other. 



The full series of individual measurements will not be printed 

 here, but the original records remain in my posession, and a com- 

 plete copy of them has been put on file at the Wistar Institute of 

 Anatomy and Biology in Philadelphia, where it may be examined 

 at any time. In the case of the condensed tables which follow, 

 it should be stated here, once for all, that the averages used are 

 always "weighted for the number of cases," while in those instances 

 where it seemed important, there is printed in parentheses along 

 with the average value, the number of measurements on which it 

 is based. The value for the internodes is always given in thou- 

 sandths of a millimeter (^). 



I. THE AVERAGE LENGTH OF THE INTERNODES AT DIFFERENT 

 LEVELS ALONG THE NERVES TO THE LEG. 



As has already been stated. Boycott '04, limited h;s observa- 

 tions to the average length of the internodes taken from one local- 

 ity, the distal end of the sciatic nerve. The attempt was therefore 

 made to determine the average length of the internodes at various 

 locahties along the nerves supplying the leg. 



Fig. I gives the arrangement of the nerves to the leg, based on a 

 dissection made by Dr. Dunn '02. The levels from which sam- 

 ples of the nerve were taken are indicated by interruptions in the 

 drawing, and designated by letters, -Sj, ^S",, S^, T, T^, T,, T^. 



The first four are from the nerve in the thigh, the fifth and sixth 

 from the nerve in the shank, and the seventh from the nerve in the 

 foot. 



In each instance a bit of the nerve was prepared according to 

 the method already described, teased as completely as possible, and 

 fifty or more measurements made on the internodes of the fibers, 

 always preferring the larger to the smaller fibers in each instance. 



