﻿art. 
  27 
  ASYMMETRY 
  IN 
  SKULLS 
  OF 
  MAMMALS 
  — 
  HOWELL 
  9 
  

  

  are 
  otherwise 
  of 
  equal 
  development, 
  it 
  is 
  impossible 
  now 
  to 
  be 
  sure 
  

   whether 
  the 
  muscles 
  passing 
  beneath 
  (within) 
  the 
  arch 
  were 
  of 
  gi 
  eater 
  

   bulk 
  upon 
  one 
  side 
  than 
  the 
  other, 
  or 
  whether 
  the 
  masseter 
  of 
  one 
  

   differed 
  somewhat 
  in 
  development 
  from 
  its 
  fellow. 
  

  

  The 
  right 
  coronoid 
  process 
  is 
  about 
  5 
  mm. 
  longer 
  than 
  the 
  left, 
  but 
  

   this 
  is 
  due 
  to 
  the 
  fact 
  that 
  the 
  mandibular 
  notch 
  is 
  correspondingly 
  

   lower 
  upon 
  that 
  side, 
  and 
  not 
  to 
  differences 
  in 
  the 
  lower-border-to- 
  

   coronoid 
  measurement. 
  The 
  reasons 
  for 
  this 
  state 
  of 
  affairs 
  are 
  too 
  

   obscure 
  and 
  complicated 
  for 
  satisfactory 
  interpretation. 
  

  

  At 
  first 
  thought 
  it 
  would 
  appear 
  that 
  the 
  displacement 
  towards 
  

   the 
  right 
  of 
  the 
  rostrum 
  is 
  attributable 
  to 
  the 
  effect 
  of 
  the 
  teeth 
  of 
  

   the 
  mandible 
  having 
  been 
  pulled 
  in 
  that 
  direction 
  by 
  the 
  action 
  of 
  

   the 
  asymmetrical 
  muscles 
  attached 
  to 
  the 
  latter. 
  Although 
  it 
  seems 
  

   that 
  this 
  hypothesis 
  should 
  be 
  the 
  logical 
  one, 
  a 
  closer 
  scrutiny 
  of 
  

   the 
  existing 
  state 
  of 
  affairs 
  demonstrates 
  that 
  the 
  rostrum 
  (i. 
  e., 
  the 
  

   portion 
  of 
  the 
  face 
  craniad 
  to 
  the 
  frontals 
  and 
  orbits) 
  primarily 
  has 
  

   been 
  deflected 
  towards 
  the 
  right. 
  The 
  reason 
  for 
  this 
  rostral 
  move- 
  

   ment 
  is 
  obscure. 
  As 
  there 
  are 
  no 
  powerful 
  muscles 
  connected 
  with 
  

   this 
  region, 
  it 
  can 
  only 
  be 
  presumed 
  that 
  the 
  displacement 
  was 
  in 
  

   response 
  to 
  certain 
  muscular 
  forces 
  operating 
  asymmetrically 
  upon 
  the 
  

   bones 
  with 
  which 
  the 
  rostrum 
  articulates. 
  It 
  is 
  clear 
  that 
  the 
  man- 
  

   dible, 
  through 
  its 
  condylar 
  articulation, 
  has 
  resisted 
  this 
  dextral 
  trend 
  

   of 
  the 
  rostrum. 
  The 
  lower 
  border 
  of 
  the 
  mandible 
  exhibits 
  a 
  tendency 
  

   to 
  remain 
  in 
  normal 
  position, 
  while 
  the 
  alveolar 
  margin, 
  in 
  response 
  

   to 
  the 
  force 
  exerted 
  by 
  the 
  teeth 
  of 
  the 
  rostrum 
  with 
  its 
  dextral 
  

   twist, 
  is 
  also 
  twisted 
  towards 
  the 
  right. 
  

  

  Extremely 
  grotesque 
  is 
  the 
  skull 
  of 
  a 
  monkey 
  (pis. 
  1 
  and 
  2) 
  — 
  Lasi- 
  

   opyga 
  griseoviridis 
  (Desmarest) 
  — 
  for 
  the 
  loan 
  of 
  which 
  I 
  am 
  indebted, 
  

   through 
  Dr. 
  G. 
  M. 
  Allen, 
  to 
  the 
  Museum 
  of 
  Comparative 
  Zoology. 
  

   This 
  is 
  a 
  fully 
  adult 
  male 
  (No. 
  15720, 
  Mus. 
  Comp. 
  Zool.), 
  bearing 
  

   the 
  data 
  "Sudan, 
  Blue 
  Nile, 
  Magangani, 
  29 
  Jan., 
  1913, 
  Phillips 
  

   Sudan 
  Ex. 
  1913, 
  Col. 
  G. 
  M. 
  Allen, 
  J. 
  C. 
  Phillips, 
  orig. 
  84". 
  Recent 
  

   injuries, 
  received 
  by 
  the 
  skull 
  at 
  the 
  time 
  when 
  the 
  specimen 
  was 
  col- 
  

   lected, 
  consist 
  of 
  the 
  breaking 
  away 
  of 
  a 
  part 
  of 
  the 
  upper 
  alveolar 
  

   border, 
  including 
  the 
  two 
  left 
  incisors, 
  and 
  injury 
  to 
  the 
  right 
  tem- 
  

   poral, 
  including 
  mastoid, 
  auditory 
  and 
  squamous 
  portions. 
  Old 
  

   osseous 
  scars 
  comprise 
  a 
  fracture 
  of 
  the 
  nasal 
  bridge, 
  which 
  probably 
  

   has 
  had 
  no 
  effect 
  upon 
  the 
  conformation 
  of 
  the 
  skull, 
  the 
  absence 
  of 
  

   the 
  right 
  lateral, 
  maxillary 
  incisor, 
  broken 
  off 
  at 
  the 
  root, 
  and 
  the 
  

   absence 
  of 
  the 
  entire 
  posterior 
  portion 
  of 
  the 
  left 
  ramus 
  of 
  the 
  man- 
  

   dible, 
  including 
  angular 
  process, 
  the 
  whole 
  condyle, 
  and 
  all 
  but 
  the 
  

   extreme 
  anterior 
  border 
  of 
  the 
  coronoid 
  process. 
  There 
  is 
  no 
  indi- 
  

   cation 
  of 
  disease, 
  so 
  it 
  is 
  likely 
  that 
  the 
  mandibular 
  fracture 
  was 
  due 
  

   to 
  an 
  accident 
  of 
  some 
  sort, 
  such 
  as 
  a 
  glancing 
  rifle 
  ball 
  or 
  a 
  long 
  fall. 
  

   The 
  portions 
  of 
  bones 
  detached 
  were 
  either 
  absorbed, 
  or 
  sloughed 
  off 
  

   53194— 
  25f 
  2 
  

  

  