﻿OF 
  THE 
  PYTHON. 
  131 
  

  

  circulation, 
  and 
  one 
  pulmonary 
  artery 
  which 
  divides 
  to 
  supply 
  the 
  two 
  

   lungs 
  ; 
  they 
  are 
  so 
  placed 
  at 
  their 
  roots, 
  as 
  to 
  form 
  an 
  arch 
  by 
  their 
  

   lateral 
  connection, 
  and 
  their 
  relative 
  situation 
  is 
  as 
  follows. 
  The 
  left 
  

   aorta, 
  the 
  smallest 
  of 
  these 
  trunks, 
  is 
  placed 
  in 
  the 
  middle 
  between 
  the 
  

   other 
  two, 
  and 
  is 
  also 
  the 
  most 
  anterior 
  ; 
  it 
  communicates 
  with 
  the 
  

   ventricle, 
  immediately 
  beneath 
  the 
  fleshy 
  column 
  just 
  described. 
  The 
  

   pulmonary 
  artery 
  is 
  situated 
  on 
  the 
  left 
  of 
  this 
  vessel, 
  and 
  is 
  much 
  

   larger 
  than 
  either 
  of 
  the 
  others; 
  it 
  opens 
  into 
  the 
  ventricle, 
  immediately 
  

   in 
  front 
  of 
  the 
  fleshy 
  column, 
  which 
  therefore 
  intervenes 
  between 
  the 
  

   orifices 
  of 
  these 
  two 
  vessels, 
  causing 
  the 
  pulmonary 
  artery 
  to 
  hold 
  com- 
  

   munication 
  with 
  the 
  anterior 
  cavity 
  of 
  the 
  ventricle, 
  as 
  formed 
  by 
  the 
  

   column, 
  and 
  the 
  left 
  aorta 
  with 
  the 
  posterior. 
  Immediately 
  behind 
  

   the 
  root 
  of 
  the 
  left 
  aorta, 
  and 
  much 
  concealed 
  by 
  it, 
  is 
  the 
  orifice 
  of 
  

   the 
  right 
  aorta,* 
  which 
  is 
  therefore 
  also 
  beneath 
  the 
  column, 
  and 
  con- 
  

   nected 
  with 
  the 
  same 
  division 
  of 
  this 
  ventricle 
  ; 
  it 
  is 
  intermediate 
  in 
  

   size 
  to 
  the 
  other 
  two. 
  From 
  this 
  arrangement 
  it 
  follows, 
  that 
  the 
  

   blood 
  which 
  is 
  thrown 
  out 
  from 
  the 
  right 
  ventricle 
  is 
  divided 
  into 
  two 
  

   columns, 
  one 
  passing 
  out 
  by 
  the 
  pulmonary 
  artery 
  in 
  front 
  of 
  the 
  fleshy 
  

   column, 
  and 
  the 
  other 
  by 
  the 
  two 
  aortse. 
  below 
  it. 
  Each 
  of 
  these 
  great 
  

   vessels 
  is 
  furnished 
  at 
  its 
  root 
  with 
  two 
  semilunar 
  valves, 
  which 
  are 
  

   calculated 
  to 
  close 
  the 
  orifice 
  of 
  communication 
  with 
  the 
  ventricle, 
  

   having 
  also 
  two 
  sinuses 
  of 
  Valsalva 
  (as 
  we 
  must 
  term 
  them) 
  to 
  be 
  filled 
  

   with 
  blood, 
  in 
  a 
  retrograde 
  movement 
  of 
  that 
  fluid. 
  The 
  mechanism, 
  

   in 
  fact, 
  excepting 
  only 
  in 
  the 
  number 
  of 
  the 
  valves, 
  is 
  like 
  that 
  of 
  the 
  

   great 
  arteries 
  of 
  the 
  human 
  heart. 
  

  

  The 
  coronary 
  arteries, 
  two 
  in 
  number, 
  arise 
  from 
  the 
  left 
  aorta, 
  and 
  

   are 
  distributed 
  upon 
  the 
  substance 
  of 
  the 
  heart; 
  the 
  coronary 
  vein, 
  

   which 
  returns 
  the 
  blood 
  from 
  these 
  arteries, 
  opens 
  into 
  the 
  right 
  auri- 
  

   cle. 
  The 
  passage 
  before 
  alluded 
  to, 
  connecting 
  the 
  two 
  ventricles, 
  

   opens 
  below 
  the 
  fleshy 
  column, 
  near 
  the 
  two 
  aortae, 
  and, 
  consequently, 
  

   in 
  direct 
  communication 
  with 
  those 
  vessels. 
  Now, 
  as 
  the 
  blood 
  that 
  

   is 
  thrown 
  out 
  from 
  the 
  left 
  ventricle, 
  passes 
  directly 
  by 
  that 
  passage 
  

   into 
  the 
  upper 
  corner 
  of 
  the 
  right 
  ventricle, 
  it 
  is 
  brought 
  at 
  once 
  to 
  

  

  * 
  The 
  terms 
  right 
  and 
  left, 
  as 
  applied 
  to 
  the 
  aortse, 
  are 
  meant 
  to 
  indicate 
  the 
  side 
  of 
  the 
  

   spine 
  along 
  which 
  the 
  artery 
  passes 
  in 
  its 
  descent 
  to 
  the 
  point 
  of 
  junction. 
  

  

  