356 Georgind Sweet : 



condition shown in Fig. 5, iii. (Sweet, '97). The duplication of 

 nerves is seen also in this one (see Text fig-ui'e 9 of the present 



Brachial and two succeeding 

 nerves of right side. 



/9^f 



paper), the anterior division running sharply forwards first 

 ventral to, then turning dorsal to, the transverse process of 

 the Ilird vertebra, and running back to accompany the posterior 

 division to its destination. 



v., VI. and VII. call for no comment, except that one may 

 rarely be absent on one or both sides — especially the 5th — 

 the vertebral column being normail in these cases. 



VIII., IX., X. and XI. are, as previously described, subject 

 t<t considerable variation. The variations show no departure 

 in general from those then given. Fig. I. (i) appears fairly 

 often, and then generally with XI. entering the sciatic nerve, 

 after the crural has been given off, us in Fig. 4 (i.). In cases 

 where XL is large, and has such an intimate relation with the 

 sciatic plexus, one is generally sure of finding a Xllth nerve, 

 indicating the more r:)rimitive condition. 



This conditi(ui is somewhat similar to that shown by Cole for 

 Rmia tempordria, without a post-coccygeal nerve, and fof R(ina 

 esculf/tita, with a i>ost-coccygeal nerve. 



A number of examples of double Vlllth nerves were found, 

 generally on one side only. They were sometimes equal in 

 size, less often the more posterior division was very fine indeed. 



As examples of the more advanced condition of this plexus 

 may be cited the following: — VIII. large, IX. normal, X. smaller 

 than usual, XL absent (cf. loc. cit.. Fig. 2, viii.). In another case 

 in which VIII. and IX. were equally large, and fused high up, to 

 form the sciatio neo-ve, the Xth and Xlth were very small in- 

 deed, and their plexus received a tiny branch from the fused 

 VIII. and IX., and at a lower level gave back to them an even 

 smaller twig. 



