﻿74 
  

  

  flow, 
  and 
  the 
  corpuscles 
  perform 
  piston-like 
  movements, 
  

   back 
  and 
  forth, 
  to 
  and 
  from 
  the 
  closed 
  ends 
  of 
  the 
  vessels, 
  at 
  

   each 
  and 
  every 
  pulsation 
  of 
  the 
  heart. 
  Sometimes 
  the 
  cor- 
  

   puscles 
  form 
  quite 
  a 
  mass 
  in 
  these 
  closed 
  vessels. 
  

  

  They 
  get 
  out 
  of 
  the 
  main 
  blood 
  flow, 
  are 
  driven 
  into 
  the 
  ves- 
  

   sels, 
  and 
  become 
  clogged 
  in 
  these 
  until 
  the 
  vessels 
  open 
  at 
  their 
  

   extremity. 
  Shortly 
  after 
  this, 
  a 
  dorsal, 
  lateral 
  communica- 
  

   tion 
  is 
  made 
  between 
  the 
  5tli 
  and 
  6th 
  vessels 
  ; 
  then 
  we 
  often 
  

   see 
  corpuscles 
  passing 
  up 
  from 
  the 
  ventral 
  aorta 
  into 
  the 
  5th 
  

   vessel, 
  and 
  from 
  this 
  through 
  the 
  new 
  channel 
  into 
  the 
  still 
  

   closed 
  6th 
  vessel 
  : 
  or 
  corpuscles 
  will 
  often 
  pass 
  into 
  the 
  6th 
  

   vessel, 
  and 
  when 
  they 
  come 
  to 
  the 
  channel 
  to 
  the 
  5th, 
  pass 
  

   into 
  it, 
  and 
  so 
  on 
  into 
  the 
  circulation. 
  It 
  is 
  only 
  a 
  short 
  

   time 
  after 
  this, 
  and 
  often 
  perhaps 
  coincident 
  with 
  the 
  form- 
  

   ation 
  of 
  tlie 
  connection 
  between 
  the 
  5th 
  and 
  6th 
  vessels, 
  that 
  

   an 
  opening 
  takes 
  place 
  in 
  the 
  median 
  line 
  of 
  the 
  ventral 
  side 
  

   of 
  the 
  united 
  6th 
  pair 
  of 
  vessels, 
  and 
  this 
  opening 
  leads 
  into 
  

   the 
  dorsal 
  aorta 
  of 
  the 
  body. 
  The 
  body 
  aorta 
  passes 
  directly 
  

   back 
  to 
  near 
  the 
  extremity 
  of 
  the 
  notochord, 
  where 
  it 
  bends 
  

   upon 
  itself 
  and 
  returns 
  as 
  the 
  vena 
  cava, 
  just 
  beneath 
  the 
  

   aorta, 
  to 
  empty 
  with 
  the 
  jugulars 
  into 
  the 
  Cuvierian 
  sinus 
  

   of 
  the 
  auricle 
  of 
  the 
  heart. 
  From 
  the 
  aorta 
  are 
  given 
  off, 
  at 
  

   different 
  parts 
  of 
  the 
  body, 
  a 
  great 
  number 
  of 
  small 
  arteries, 
  

   which 
  are 
  distributed 
  to 
  different 
  parts 
  of 
  the 
  body. 
  In 
  

   most 
  fish 
  and 
  other 
  vertebrata, 
  the 
  principal 
  arterips 
  thus 
  

   given 
  off 
  in 
  the 
  embryo 
  are 
  the 
  omphalo-meseraic 
  arteries, 
  

   which 
  pass 
  to 
  and 
  over 
  the 
  vitellus. 
  In 
  tlic 
  Trout 
  and 
  Sal- 
  

   mon 
  there 
  are 
  two 
  of 
  these 
  arterie:-^, 
  one, 
  the 
  most 
  anterior, 
  

   passing 
  directly 
  to 
  the 
  yolk, 
  a 
  second 
  passing 
  along 
  the 
  

   upper 
  side 
  of 
  the 
  intestine, 
  supplying 
  it 
  Avith 
  blood, 
  and 
  

   returning 
  along 
  its 
  ventral 
  side, 
  to 
  unite 
  with 
  the 
  first 
  om- 
  

   phalo-meseraic 
  artery, 
  and 
  then, 
  dividing 
  into 
  innumerable 
  

   capillaries, 
  pass 
  over 
  the 
  vitellus, 
  to 
  be 
  gathered 
  together 
  

   once 
  more, 
  and 
  empty 
  their 
  contents 
  through 
  the 
  omphalo- 
  

   meseraic 
  vein 
  or 
  veins 
  — 
  sometimes 
  there 
  is 
  only 
  one, 
  some- 
  

   times 
  two 
  — 
  into 
  the 
  Cuvierian 
  sinus 
  of 
  the 
  auricle. 
  In 
  the 
  

  

  