﻿470 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [44] 
  

  

  The 
  filum 
  terminate 
  passes 
  back 
  into 
  the 
  vertebral 
  canal 
  for 
  a 
  shcrt 
  dis- 
  

   tance 
  and 
  is 
  lost. 
  The 
  origins 
  of 
  the 
  spinal 
  nerves 
  are 
  crowded 
  together 
  

   in 
  the 
  cervical 
  region 
  in 
  correspondence 
  with 
  the 
  shortening 
  of 
  the 
  ver- 
  

   tebrae 
  of 
  this 
  portion 
  of 
  the 
  column. 
  In 
  the 
  dorsal 
  region 
  the 
  origins 
  

   of 
  the 
  pairs 
  are 
  farther 
  apart, 
  but 
  from 
  the 
  lumbar 
  enlargement 
  back- 
  

   ward 
  they 
  are 
  much 
  crowded 
  together. 
  The 
  seventh, 
  eighth, 
  ninth, 
  

   tenth, 
  and 
  eleventh 
  pairs 
  of 
  the 
  lumbo-caudal 
  nerves 
  unite 
  to 
  form 
  the 
  

   genital 
  or 
  internal 
  pudic, 
  but 
  as 
  there 
  is 
  no 
  functionally 
  mobile 
  hind 
  

   limb, 
  the 
  branches 
  corresponding 
  to 
  the 
  genito-crural, 
  obturator, 
  ex- 
  

   ternal 
  cutaneous, 
  anterior 
  crural 
  and 
  sciatic 
  are 
  absent. 
  The 
  internal 
  

   pudic 
  is 
  well 
  represented. 
  Small 
  twigs 
  only 
  from 
  the 
  seventh 
  and 
  

   eleventh 
  lumbo-caudal 
  pairs 
  enter 
  into 
  the 
  formation 
  of 
  this 
  nerve. 
  It 
  

   pierces 
  the 
  great 
  inferior 
  lumbo-caudal 
  muscular 
  mass, 
  and 
  passing 
  

   obliquely 
  backward 
  through 
  it 
  divides 
  inferiorly 
  into 
  several 
  branches 
  

   which 
  innervate 
  the 
  reproductive 
  organs. 
  

  

  Erom 
  the 
  eleventh 
  lumbo-caudal 
  pair 
  all 
  the 
  inferior 
  divisions 
  join 
  to 
  

   form 
  the 
  inferior 
  longitudinal 
  cord 
  or 
  plexus, 
  the 
  last 
  pair 
  entering 
  the 
  

   lower 
  cord 
  opposite 
  the 
  twenty-sixth 
  lumbo-caudal 
  vertebra. 
  The 
  in- 
  

   ferior 
  lumbo-caudal 
  cord 
  supplies 
  the 
  psoas 
  or 
  infracaudal 
  muscles 
  in 
  

   Cetacea 
  the 
  same 
  as 
  do 
  the 
  iliohypogastric 
  and 
  ilioinguinal 
  nerves 
  in 
  

   man. 
  

  

  The 
  hinder 
  pairs 
  which 
  go 
  to 
  form 
  the 
  great 
  inferior 
  and 
  superior 
  

   lateral 
  cords, 
  the 
  first 
  above 
  the 
  latter 
  below 
  the 
  transverse 
  processes, 
  

   pass 
  backwards 
  for 
  a 
  long 
  distance, 
  the 
  hinder 
  ones 
  for 
  about 
  tue 
  extent 
  

   of 
  nineteen 
  vertebras 
  as 
  a 
  strongly 
  developed 
  bundle 
  or 
  cauda 
  equina, 
  

   twigs 
  from 
  which 
  pass 
  out 
  on 
  either 
  side, 
  a 
  dorsal 
  one 
  to 
  the 
  dorsal 
  cord, 
  

   and 
  a 
  ventral 
  one 
  to 
  the 
  ventral 
  cord, 
  through 
  the 
  intervals 
  between 
  

   the 
  neural 
  arches 
  of 
  the 
  lumbo-caudal 
  vertebras. 
  The 
  ventral 
  twigs 
  

   pass 
  down 
  between 
  the 
  transverse 
  processes. 
  

  

  The 
  four 
  great 
  lumbo-caudal 
  cords, 
  two 
  above 
  the 
  transverse 
  pro- 
  

   cesses 
  and 
  two 
  below 
  them 
  in 
  the 
  porpoise, 
  judging 
  from 
  the 
  muscles 
  

   which 
  they 
  innervate 
  in 
  the 
  latter, 
  are 
  respectively 
  the 
  homologues 
  of 
  

   the 
  ' 
  ; 
  posterior 
  "and 
  "anterior 
  "branches 
  of 
  thelumbar 
  nerves 
  in 
  man. 
  Un- 
  

   like 
  the 
  latter, 
  however, 
  in 
  consequence 
  of 
  the 
  great 
  bulk 
  of 
  the 
  dorsal 
  

   extensors 
  of 
  the 
  tail, 
  longissimus 
  dorsi, 
  erectores 
  spince, 
  and 
  multiftdus 
  

   spina', 
  there 
  has 
  also 
  been 
  a 
  dorsal 
  plexus 
  differentiated 
  which 
  leads 
  to 
  

   the 
  formation 
  of 
  the 
  dorsal 
  lumbo-caudal 
  cord. 
  Inferiorly 
  the 
  plexus 
  

   has 
  not 
  the 
  limited 
  extent 
  posteriorly 
  as 
  found 
  in 
  man 
  where 
  it 
  is 
  par- 
  

   tially 
  represented 
  by 
  the 
  lumbo- 
  sacral 
  cord, 
  but 
  is 
  extended 
  backwards 
  

   quite 
  to 
  the 
  flukes, 
  as 
  the 
  inferior 
  lumbo-caudal 
  cord. 
  

  

  Comparing 
  the 
  nervous 
  system 
  of 
  the 
  fish 
  and 
  cetacean, 
  Cunningham 
  

   remarks 
  : 
  " 
  From 
  the 
  spinal 
  cord 
  passing 
  so 
  far 
  back 
  in 
  the 
  vertebral 
  

   canal 
  (in 
  the 
  former) 
  it 
  follows 
  that 
  the 
  nerves 
  which 
  supply 
  the 
  caudal 
  

   apparatus 
  have 
  a 
  very 
  short 
  course 
  to 
  run 
  from 
  their 
  points 
  of 
  origin 
  to 
  

   their 
  distribution. 
  Very 
  different 
  is 
  the 
  arrangement 
  of 
  the 
  corre- 
  

   sponding 
  nerves 
  in 
  the 
  Cetacea, 
  which 
  spring 
  from 
  the 
  lumbar 
  enlarge- 
  

  

  