﻿328 
  FRANCIS 
  H. 
  A. 
  MARSHALL. 
  

  

  Ovulation. 
  

  

  So 
  far 
  as 
  my 
  observations 
  go, 
  ovulation 
  in 
  the 
  case 
  of 
  the 
  

   ferret 
  probably 
  takes 
  place 
  at 
  the 
  beginning 
  of 
  the 
  period 
  of 
  

   oestrus, 
  but 
  only 
  as 
  a 
  result 
  of 
  coition. 
  If 
  the 
  female 
  is 
  not 
  

   allowed 
  to 
  copulate 
  the 
  mature 
  follicles 
  and 
  contained 
  ova 
  

   appear 
  to 
  undergo 
  atresia, 
  notwithstanding 
  the 
  continuance 
  

   of 
  the 
  oestrus. 
  As 
  a 
  consequence 
  the 
  female 
  fails 
  to 
  become 
  

   pregnant 
  if 
  warded 
  too 
  late 
  in 
  the 
  season. 
  Thus 
  the 
  per- 
  

   sistence 
  of 
  the 
  oestrus, 
  which 
  may 
  continue 
  far 
  into 
  tlie 
  

   recuperative 
  period 
  of 
  the 
  uterus, 
  or 
  even 
  beyond 
  it, 
  is 
  asso- 
  

   ciated 
  with 
  degenerate 
  follicles 
  in 
  the 
  ovary. 
  These 
  facts 
  

   may 
  perhaps 
  afford 
  an 
  explanation 
  of 
  the 
  observations 
  made 
  

   by 
  Robinson 
  (1893), 
  who 
  found 
  that, 
  with 
  the 
  ferrets 
  em- 
  

   ployed 
  in 
  his 
  investigation, 
  coition 
  very 
  frequently 
  did 
  not 
  

   result 
  in 
  pregnancy, 
  although 
  the 
  animals 
  might 
  have 
  copu- 
  

   lated 
  more 
  than 
  once 
  during 
  oestrus. 
  

  

  The 
  extension 
  of 
  the 
  period 
  of 
  oestrus 
  under 
  conditions 
  

   such 
  as 
  to 
  preclude 
  the 
  possibility 
  of 
  the 
  occurrence 
  of 
  preg- 
  

   nancy 
  can 
  only 
  be 
  regarded 
  as 
  one 
  of 
  those 
  " 
  disharmonies" 
  

   in 
  the 
  apparatus 
  of 
  reproduction 
  upon 
  the 
  existence 
  of 
  which 
  

   in 
  the 
  animal 
  and 
  human 
  organisation 
  Metchnikoff 
  in 
  his 
  

   recent 
  work 
  (1903) 
  has 
  laid 
  so 
  much 
  stress. 
  

  

  A 
  bitch 
  ferret 
  which 
  I 
  artificially 
  inseminated 
  failed 
  to 
  

   become 
  pregnant, 
  owing 
  probably 
  to 
  the 
  presence 
  of 
  the 
  

   spermatozoa 
  in 
  the 
  uterus 
  Avithout 
  the 
  additional 
  stimulus 
  of 
  

   coition 
  failing 
  to 
  induce 
  ovulation 
  ; 
  but 
  it 
  may 
  have 
  been 
  in 
  

   this 
  case 
  also 
  that 
  the 
  mature 
  Graafian 
  follicles 
  had 
  begun 
  to 
  

   degenerate, 
  and 
  that 
  the 
  season 
  for 
  ovulation 
  had 
  passed 
  by. 
  

  

  In 
  failing 
  to 
  ovulate 
  during 
  oestrus 
  except 
  as 
  a 
  result 
  of 
  

   coition 
  the 
  fem'et 
  resembles 
  the 
  rabbit 
  in 
  some 
  cases 
  at 
  any 
  

   rate 
  (Heape, 
  1897), 
  and 
  the 
  sheep 
  more 
  exceptiouMlly 
  

   (Marshall, 
  1903). 
  The 
  majority 
  of 
  the 
  mammalia 
  in 
  which 
  

   the 
  subject 
  has 
  been 
  investigated 
  have 
  been 
  found 
  to 
  ovulate 
  

   spontaneously 
  when 
  " 
  on 
  heat." 
  

  

  Fig. 
  9 
  represents 
  a 
  section 
  through 
  an 
  atretic 
  follicle 
  from 
  

   a 
  ferret 
  in 
  which 
  oestrus 
  had 
  lasted 
  for 
  at 
  least 
  three 
  weeks, 
  

  

  