28C Proceedings of the Royal Society of Victoria. 



In form i. (Fig. 3), we see the sciatic composed chiefly of X. 

 fibres assisted by some from IX., having none from VIII. In 

 forms ii., iii., and iv., X. and IX. enter almost equally into the 

 composition of the sciatic nerve, in form ii. some fibres from XI. 

 enter this union, in iii. we have only X. and IX., in iv. we have 

 the first appearance of VIII. fibres in this nerve. Form v., the 

 most advanced according to Table K, might have been allotted 

 that position by inference from the advance of the four previous 

 forms as seen in the figure, since in it we find the sciatic with 

 a majority of IX. fibres, and also a constant presence of VIII. 

 fibres, X. sinking to a third place in this respect. A further 

 explanation of the irregularity in the maximum percentage 

 frequency in Table K here suggests itself. Just as we And 

 forms ii., iii., and iv., form a complete series in themselves in 

 the table, so we find from the figures that this is also the case, 

 all three coming under a general description, viz., possessing 

 equal quantities of X. and IX. fibres, which forms an inter- 

 mediate stage between form i. with a majority of X. fibres, and 

 form v. with a majority of IX. fibres. 



Table G does not appear to give us any evidence beyond the 

 fact that form i., which we have found to be the most primitive, 

 occurs with a lower thickness than form v., the most advanced. 

 Table H on the other hand shows a well-marked order agreeing 

 with that proved from Table F and Fig. 3. Since nerve X. 

 was found to be in a state of decreasing thickness the most 

 primitive composition of the sciatic ought to occur chiefly with 

 the higher thicknesses, and the more advanced forms in a 

 definite order with the decrease in thickness. Such is the case. 

 Excluding the isolated cases in thickness 11 we find that form 

 i. occurs most frequently with thickness 10, form ii. with 

 thickness 11 and then thickness 9, form iii. with thickness 8, 

 form iv. with thickness 6, and form v. with thickness 3. 



Table K showing the relations between the thicknesses of XL 

 and the composition of the sciatic offers a further confirmation 

 of those results, since we find that XI. being in a decreasing 

 condition, form i. occurs most frequently with thickness 5, form 

 ii. with thickness 5, form iii. with thickness 3, excluding an 

 isolated case in thickness 1, form iv. with thicknesses 2 and 1, 

 while form v. chiefly occurs with thickness 2. 



