﻿abt. 
  27 
  ASYMMETRY 
  IN 
  SKULLS 
  OF 
  MAMMALS 
  — 
  HOWELL 
  17 
  

  

  of 
  the 
  temporals 
  [andjmasseters, 
  but 
  such 
  a 
  condition 
  of 
  the 
  face, 
  11 
  

   when 
  marked, 
  can 
  not 
  be 
  due 
  primarily 
  to 
  myological 
  stimuli. 
  It 
  

   may 
  be 
  attributable 
  iirst 
  to 
  a 
  setting 
  out 
  of 
  plane, 
  through 
  nongrowth 
  

   of 
  one 
  side, 
  of 
  the 
  bones 
  with 
  which 
  the 
  rostrum 
  articulates, 
  as 
  a 
  

   house 
  may 
  be 
  thrown 
  out 
  of 
  plumb 
  by 
  the 
  settling 
  of 
  one 
  side 
  of 
  its 
  

   foundation; 
  or 
  it 
  may 
  be 
  due 
  to 
  the 
  pull, 
  through 
  the 
  interlocking 
  

   of 
  the 
  canines, 
  primarily 
  exerted 
  by 
  a 
  glenoid 
  fossa, 
  and 
  hence 
  the 
  

   mandible, 
  which 
  has 
  been 
  displaced. 
  

  

  Asymmetry 
  of 
  the 
  occipital 
  plane 
  may 
  be 
  ascribable 
  in 
  part 
  to 
  

   differences 
  in 
  the 
  size 
  of 
  the 
  lambdoidal 
  crests 
  induced 
  either 
  by 
  the 
  

   temporal 
  muscles, 
  or 
  by 
  variation 
  in 
  certain 
  of 
  the 
  cervical 
  muscles, 
  

   or 
  both. 
  As 
  only 
  the 
  insertions, 
  and 
  not 
  the 
  origins, 
  of 
  the 
  latter 
  

   are 
  available 
  for 
  examination, 
  interpretation 
  of 
  the 
  few 
  facts 
  presented 
  

   is 
  difficult. 
  

  

  The 
  form 
  of 
  an 
  asymmetrical 
  mandible 
  is 
  determined 
  mostly 
  by 
  

   the 
  positions 
  of 
  the 
  glenoid 
  fossae 
  at 
  one 
  extreme, 
  and 
  by 
  the 
  force 
  

   that 
  may 
  be 
  exerted 
  by 
  the 
  interlocking 
  canines 
  at 
  the 
  other. 
  Vari- 
  

   ation 
  in 
  size 
  between 
  the 
  mandibular 
  processes 
  of 
  the 
  two 
  rami 
  is 
  

   not 
  likely 
  to 
  be 
  as 
  great 
  as 
  are 
  certain 
  asymmetrical 
  differences 
  in 
  

   the 
  skull 
  proper. 
  In 
  other 
  words, 
  the 
  muscular 
  origins 
  seem 
  to 
  be 
  

   more 
  sensitive 
  to 
  asymmetrical 
  influences 
  than 
  are 
  their 
  insertions. 
  

   Asymmetry 
  of 
  the 
  mandible, 
  in 
  fact, 
  seems 
  to 
  be 
  due 
  chiefly 
  to 
  

   mechanical 
  stimuli. 
  

  

  11 
  For 
  convenience 
  the 
  posterior 
  portions 
  of 
  the 
  zygomatic 
  processes 
  of 
  the 
  maxillse 
  are 
  here 
  considered 
  

   as 
  not 
  belonging 
  to 
  the 
  face 
  proper. 
  

  

  