138 MKIMSTN. 1 VARIATION". [PART I. 



IXth (instead of Vlllrh alone, as seen in five cases outof six). 

 But 1 !i"U_di in all these respects the nerve-supply of the plexus was 

 in ordinal position posterior to the normal, nevertheless the 1\ th 

 a cMinmunieation to the Vth (as it does normally) and the 

 Buprascapular and subscapular were given off normally. Here, then, 

 the -upply to the plexus began at the normal place, though it ex- 

 tended further back than it normally does. On the right side the 

 branch from th- Xth was slightly bigger than usual, but otherwise 



th dy abnormality noted was that the IXth sent a branch to the 



miisculo-xpjral. 1 1 I;I;I:I\<;M \M. W. P.. Proc. Roy. Soc., 1886, XLI. 



P :;.".. In \iew of FURBRINGEE'S evidence (see Nos. 65 and (i~), 

 it iiii^lit be expected that the first rib would be reduced in corre- 

 lation with the irregular forward Homceosis of the nerves. In 

 replv however to a question on the subject, Dr Herringham has 

 kindly informed me that no abnormality in the ribs was seen, but 

 thai this point was not specially considered. 



( 'oinpare also L\\i.s case, No. '24, in which similarly a large 

 branch from the Xth joined the plexus on the right side and the 

 firs) rib was rudimentary, both structures thus shewing a correla- 

 ted forward I b >mO3< isis. 



LI \li:n-s.\ci:AL PLEXUS. 



*70. r,\ ph\ -i"l'. -leal methods SHERRINGTON found that the supply 



to i iie lumbo-sacral jilcxus \aried considerably with regard to its 

 origin from the spinal nerves. This was seen in Macacus, in the 

 1 and in the Frog. In none of these animals was any one ar- 

 ran-'-nient found sufficient ly often to justify its selection as a"nor- 

 mal type. In each case it was found convenient to divide the 

 dit'f. rent forms of arrangement into two classes, the one in which 

 the -upply to the pi. AIIS uas in ordinal position more anterior 

 ("pie-axial." Sherrini;toni. tl ther being more posterior ("post- 

 axial." Sherrin-toii . Particulars respecting the distribution of the 

 ial nerves and the movements resulting from their stimulation 

 in the two classes, are ^\\<-\\ in detail (i|. v.). In Macacus, 31 in- 

 li\idua|s bel'.n^ed to the nioiv a 1 1 1 e i' i , ,] ( la ss, and 21 to the more 



posterior. In the ( 'at the number of individuals in the two classes 

 was -- and :!!l respectively. It is stated generally that 



'I'll.- iliMrilnitioii of tin- peripheral nerve t nniks is not obviously 

 iliH'rivnt, \\liether, I y iis rooi f,niiatiitii the plexus In-long to the 

 pre-axial class, or to the p.-i axial. The peripheral nerve-trunks are, 



D o-.l- th.-ir OlUScleS, relatively stable in eomp.-iri.son with the spinal 



! \\"hen the inin-rvation of the liiiili-inuseles is of the pre-axial 



. also i- that ..t' the anus, vagina and bladder; and conversely/' 



SHERRINOTON, < '. 8., Proc. A'.-//. Soc., l^'.'i', i.i. pp. 7<i 76. 



71. Primates. Si ..... m examining the tacts of Variation we are 

 g for evidence as t,, the m..des in which specific differences 



