500 M. J. GKEENMAN 



measurements for the ten largest fibers of the distal ends are 

 85 square micra, 85.8 square micra and 113 square micra re- 

 spectively. We thus observe that the size of fibers diminishes 

 from the proximal to the distal ends, this diminution averaging 

 about 29 per cent of the proximal measurements, in a distance 

 of 10 mm. — the length of nerve excised. Combining these aver- 

 ages of the proximal and distal ends, we have 113.6 square 

 micra as the average sectional area for the ten largest fibers in 

 the middle zone of the nerve. 



We observe also from table 9, that the sectional area of fibers 

 increases as the weight of the animal increases. Taking weight 

 as an index of age we may infer that in young animals nerve 

 fibers increase in sectional area with the age of the animal. 



SECTIONAL AREAS OF NERVE FIBERS FROM THE CONTROL SIDE 

 OF OPERATED ANIMALS 



Series 7, including operated anunals nos. 106, 114 and 154, 

 was utilized for the determination of sectional areas of the fibers 

 of the control nerves and the sectional areas of fibers of the 

 proximal and distal ends of the operated nerves. 



Forty or more of the largest fibers from each control nerve 

 and from each proximal and each distal end of each operated 

 nerve were measured. The measurements were tabulated under 

 their proper headings in the order of their size beginning with 

 the largest fibers. From this tabulation the averages of each 

 successive group of ten fibers, beginning with the largest, were 

 taken, the percentage value of the axis was determined for each 

 group and the data arranged in table 10. 



From the table we note that the average for the control fibers 

 in group 1 is 65.7 square micra. The average weight of the 

 three animals is 156 grams and their average age is 189 days. 

 From table 9, we find that the average sectional area of the 

 proximal and distal ends of the 10 largest fibers of three normal 

 animals, of an average weight of 135 grams, is 113.6 square 

 micra or an excess of 47.9 square micra over the controls of the 



