﻿STRUCTURE 
  OF 
  THE 
  STOMACH. 
  213 
  

  

  canal 
  is 
  our 
  present 
  knowledge 
  so 
  unsatisfactory 
  as 
  of 
  this. 
  The 
  few 
  

   observations 
  that 
  have 
  been 
  made 
  are 
  eminently 
  incomplete. 
  It 
  is 
  

   known 
  that 
  there 
  is 
  no 
  thick 
  cuticula 
  ; 
  that 
  the 
  muscular 
  layers 
  are 
  less 
  

   powerful 
  than 
  in 
  other 
  parts, 
  and 
  certain 
  other 
  details, 
  which 
  a 
  brief 
  ex- 
  

   amination 
  suffices 
  to 
  clear 
  up. 
  Frey 
  and 
  Leuckart 
  297 
  pointed 
  out 
  that 
  the 
  

   walls 
  of 
  the 
  stomach 
  were 
  not 
  folded, 
  but 
  that 
  the 
  secretory 
  surface 
  was 
  

   increased 
  in 
  some 
  cases 
  (in 
  many 
  Coleoptera, 
  for 
  instance) 
  by 
  the 
  epithe- 
  

   lium 
  and 
  connective 
  tissue 
  forming 
  villi, 
  a 
  fact 
  already 
  noticed 
  by 
  H. 
  

   Meckel. 
  298 
  Sirodot 
  299 
  subsequently 
  showed 
  that 
  there 
  are 
  also 
  gastric 
  

   glands 
  in 
  many 
  insects, 
  and 
  describes 
  particularly 
  (1. 
  c, 
  pi. 
  13, 
  Fig. 
  3) 
  

   how 
  in 
  the 
  field 
  cricket 
  the 
  gastric 
  follicles 
  occupy 
  the 
  interspaces 
  of 
  a 
  

   network 
  formed 
  by 
  the 
  sinuous 
  fibers 
  of 
  the 
  connective 
  tissue, 
  " 
  tunica 
  

   propria 
  " 
  auct. 
  I 
  have 
  found 
  essentially 
  the 
  same 
  structure 
  to 
  exist 
  in 
  

   grasshoppers 
  (Caloptenus 
  and 
  Oedipoda). 
  The 
  description 
  of 
  the 
  

   minute 
  anatomy 
  of 
  the 
  ventriculus 
  which 
  Leydig 
  gives 
  300 
  is 
  very 
  meager 
  

   and 
  insufficient, 
  while 
  that 
  given 
  of 
  the 
  epithelium 
  and 
  glands 
  in 
  the 
  

   stomach 
  of 
  the 
  cockroach 
  by 
  von 
  Basch 
  301 
  will 
  probably 
  require 
  some 
  

   modification. 
  

  

  The 
  walls 
  of 
  the 
  stomach 
  are 
  composed 
  of 
  an 
  internal 
  epithelium, 
  a 
  

   layer 
  of 
  connective 
  tissue, 
  an 
  inner 
  layer 
  of 
  unstriated 
  circular 
  muscu- 
  

   lar 
  fibres, 
  and 
  an 
  external 
  layer 
  of 
  longitudinal 
  fibres 
  of 
  striated 
  muscle. 
  

   In 
  studying 
  these 
  layers 
  I 
  have 
  found 
  it 
  best 
  to 
  begin 
  by 
  viewing 
  them 
  

   from 
  the 
  inner 
  surface. 
  If 
  the 
  walls 
  of 
  the 
  stomach 
  be 
  spread 
  out 
  and 
  

   stained 
  and 
  then 
  mounted 
  in 
  glycerine 
  or 
  Canada 
  balsam, 
  it 
  will 
  be 
  seen 
  

   that 
  the 
  nuclei 
  of 
  the 
  epithelium 
  are 
  not 
  uniformly 
  distributed, 
  but 
  there 
  

   are 
  little 
  clusters, 
  each 
  of 
  which 
  corresponds 
  to 
  a 
  small 
  gland 
  or 
  follicle 
  ; 
  

   it 
  can 
  be 
  further 
  seen 
  that 
  each 
  gland 
  has 
  a 
  cavity 
  or 
  duct 
  ; 
  each 
  follicle 
  

   lies 
  in 
  a 
  cup 
  of 
  connective 
  tissue, 
  which 
  separates 
  it 
  from 
  its 
  neighbors. 
  

   If 
  a 
  piece 
  of 
  the 
  wall 
  spread 
  out 
  on 
  a 
  glass 
  slide 
  in 
  a 
  drop 
  or 
  two 
  of 
  

   water, 
  is 
  gently 
  brushed 
  with 
  a 
  fine 
  camel's 
  hair 
  pencil, 
  the 
  epithelium 
  

   can 
  be 
  removed, 
  and 
  if 
  the 
  specimen 
  be 
  then 
  stained 
  and 
  mounted 
  the 
  

   structure 
  of 
  the 
  remaining 
  layers 
  will 
  be 
  displayed 
  as 
  shown 
  in 
  Fig. 
  39. 
  

   The 
  connective 
  tissue, 
  tunica 
  propria, 
  forms 
  a 
  somewhat 
  irregular 
  net- 
  

   work, 
  302 
  the 
  meshes 
  of 
  which 
  vary 
  in 
  size 
  only 
  between 
  certain 
  limits. 
  In 
  

   the 
  figure 
  the 
  network 
  is 
  drawn 
  somewhat 
  darker 
  than 
  it 
  appears 
  in 
  

   reality, 
  in 
  order 
  to 
  make 
  it 
  stand 
  out 
  more 
  plainly. 
  The 
  spaces 
  of 
  the 
  

   network 
  are 
  the 
  cups 
  before 
  mentioned 
  in 
  which 
  the 
  gastric 
  fol- 
  

   licles 
  lie. 
  The 
  tissue 
  has 
  a 
  fibrous 
  character 
  and 
  also 
  forms 
  the 
  bottoms 
  

   of 
  the 
  cups, 
  as 
  is 
  shown 
  by 
  sections. 
  Underneath 
  the 
  connective 
  tissue 
  

   follows 
  the 
  internal 
  muscular 
  coat, 
  In. 
  m., 
  composed 
  of 
  a 
  great 
  number 
  

  

  297 
  Frey 
  und 
  Leuckart 
  : 
  Anat. 
  Physiol. 
  Ubersicht. 
  Thierreichs, 
  1855, 
  p. 
  114. 
  

  

  298 
  Meckel. 
  Mikrographie 
  einiger 
  Driisenapparate 
  niederer 
  Seethiere. 
  Muller's 
  Arch., 
  1846. 
  Die 
  Ein- 
  

   theilung 
  des 
  Darmcanals 
  bei 
  den 
  Insekten. 
  Par. 
  4, 
  p. 
  23. 
  

  

  299 
  Sirodot 
  Recherches 
  surles 
  secretions 
  chez 
  les 
  Insectes. 
  Ann. 
  Sci. 
  Nat. 
  Zool. 
  Ser. 
  4. 
  Tome 
  X, 
  p. 
  

   183 
  (1858). 
  

  

  300 
  Leydig. 
  Lehrbuch 
  der 
  Histologic 
  1858, 
  p. 
  337. 
  

  

  301 
  Basch, 
  1. 
  c, 
  Wien. 
  Akad. 
  Sitzber., 
  xxxiii, 
  248,ff 
  

   ** 
  Compare 
  Sirodot, 
  1. 
  c, 
  PI. 
  13, 
  Fig. 
  3. 
  

  

  