Variations in Spinal N&rves of Hyla awrea. 285 



we see that the three most primitive forms i., ii., iii., occur 

 with lower thicknesses than the most advanced (viii.). 



Tables F, G, H and K, were compiled for the purpose of 

 ascertaining whether the variations in the composition of the 

 sciatic nerve, bear any relation to the variation in thickness of 

 any component nerve. 



I find that with the thickness of VIII. (Table F), the only 

 relations noticeable are that form i., which is evidently the most 

 primitive from its occurrence only with two of the smaller 

 thicknesses of nerve VIII., occurs most frequently with a 

 smaller thickness than does form v., which must be the most 

 advanced, since it does not occur with the two smallest thick- 

 nesses of VIII. In the three intermediate forms there is a 

 distinct increase in the thickness with which each of the three 

 forms occur most frequently, i.e., form ii. is found most often 

 with thickness 3, form iii. with thickness 4, and form iv. with 

 thickness 7. Thus, although the table as a whole appears 

 somewhat irregular, these two parts would seem to show a 

 distinct advancement pari passu with an increase in thickness. 

 The absence of a strict progression is scarcely to be wondered 

 at, since VIII. really only takes any share in the formation of 

 the sciatic in two out of the five forms. This will be clear on 

 reference to Fi<* 4. 



I W 



^tTT 



In this it will be seen that the progression found in Table F, 

 when compared with the five figures of the forms of that table, 

 offers a confirmation of the forward transference of function 

 found in connection with the cruralis and ileo-hypogastric nerves. 



