﻿(ESTROUS 
  CYCLE 
  IN 
  THE 
  COMMON 
  FERRET. 
  339 
  

  

  at 
  first 
  larger 
  in 
  size 
  than 
  at 
  any 
  other 
  time 
  throughout 
  the 
  

   cycle. 
  

  

  The 
  character 
  of 
  the 
  changes 
  described 
  affords 
  further 
  

   proof 
  of 
  the 
  homology 
  between 
  the 
  menstrual 
  cycle 
  of 
  the 
  

   primates 
  and 
  the 
  oestrous 
  cycle 
  of 
  the 
  lower 
  mammalia, 
  the 
  

   processes 
  which 
  occur 
  in 
  the 
  uterus 
  of 
  the 
  ferret 
  during 
  the 
  

   cycle 
  being 
  essentially 
  similar 
  to 
  those 
  which 
  take 
  place 
  in 
  the 
  

   monkey 
  (Heape, 
  1894, 
  1897), 
  the 
  bitch 
  (Retterer, 
  1892), 
  and 
  

   the 
  sheep 
  (Marshall, 
  1903). 
  

  

  Ovulation 
  occurs 
  probably 
  at 
  the 
  commencement 
  of 
  the 
  

   oestrous 
  period, 
  but 
  only 
  as 
  a 
  result 
  of 
  sexual 
  intercourse. 
  An 
  

   attempt 
  to 
  induce 
  pregnancy 
  by 
  artificial 
  insemination 
  was 
  a 
  

   failure, 
  the 
  mere 
  presence 
  of 
  the 
  sperms 
  in 
  the 
  uterus 
  being 
  

   apparently 
  insufficient 
  to 
  produce 
  the 
  stimulus 
  necessary 
  for 
  

   ovulation. 
  But 
  while 
  ovulation 
  does 
  not 
  appear 
  to 
  take 
  place 
  

   in 
  the 
  absence 
  of 
  coition, 
  the 
  oestrus 
  continues 
  for 
  a 
  consider- 
  

   able 
  period 
  after 
  that 
  the 
  time 
  for 
  ovulation 
  has 
  passed 
  by, 
  

   so 
  that 
  the 
  persistence 
  of 
  the 
  oestrus 
  is 
  associated 
  with 
  the 
  

   presence 
  of 
  atretic 
  follicles 
  in 
  the 
  ovary. 
  

  

  Since 
  coition 
  and 
  ovulation 
  take 
  place 
  after 
  the 
  pro-oestrum, 
  

   it 
  is 
  clear 
  that 
  the 
  degeneration 
  stages 
  of 
  the 
  pro-oestrnni 
  

   cannot 
  be 
  of 
  the 
  nature 
  of 
  an 
  undoing, 
  in 
  consequence 
  of 
  the 
  

   absence 
  of 
  a 
  fertilised 
  ovum, 
  of 
  preparations 
  made 
  during 
  the 
  

   earlier 
  growth 
  stages. 
  

  

  Fraenkel, 
  however, 
  in 
  a 
  recent 
  paperr(1903) 
  adopts 
  the 
  

   view 
  that 
  the 
  phenomena 
  of 
  menstruation, 
  which 
  has 
  been 
  

   shown 
  to 
  be 
  homologous 
  with 
  the 
  pro-oestrum, 
  are 
  brought 
  

   about 
  by 
  the 
  secretory 
  activity 
  of 
  the 
  corpus 
  luteum.^ 
  This 
  

   hypothesis, 
  in 
  the 
  light 
  of 
  the 
  facts 
  stated 
  above, 
  appears 
  to 
  

  

  ' 
  According 
  to 
  Eraenkel 
  tlie 
  corpus 
  luteum 
  is 
  the 
  organ 
  of 
  internal 
  

   secretion 
  in 
  the 
  ovary, 
  and 
  controls 
  the 
  nutrition 
  of 
  the 
  uterus, 
  not 
  only 
  

   during 
  pregnancy, 
  but 
  throughout 
  tlie 
  whole 
  cycle, 
  there 
  being, 
  properly 
  

   speaking, 
  but 
  one 
  corpus 
  luteum, 
  which 
  renews 
  itself 
  in 
  slightly 
  different 
  

   positions, 
  in 
  the 
  case 
  of 
  tlie 
  human 
  subject 
  at 
  montlily 
  intervals. 
  According 
  

   to 
  this 
  somewhat 
  extended 
  view 
  of 
  the 
  nature 
  of 
  the 
  corpus 
  luteum, 
  it 
  would 
  

   seem 
  that 
  the 
  secretions 
  of 
  tiiat 
  organ 
  must 
  be 
  regarded 
  as 
  varying 
  from 
  time 
  

   to 
  time 
  both 
  in 
  character 
  and 
  quantity, 
  to 
  account 
  for 
  the 
  changes 
  which 
  take 
  

   place 
  during 
  the 
  uterine 
  cycle. 
  

  

  