﻿(ESTROUS 
  CYCLE 
  IN 
  THE 
  COMMON 
  FERRET. 
  341 
  

  

  tliat 
  the 
  pro-oestrum 
  occurs 
  as 
  a 
  result 
  of 
  ovulation, 
  or 
  is 
  

   brought 
  about 
  by 
  tlie 
  pressure 
  of 
  the 
  growing 
  Graafian 
  

   follicles 
  on 
  the 
  nerve-endings, 
  as 
  supposed 
  by 
  Strassmann 
  

   (1896). 
  

  

  There 
  are 
  other 
  considerations 
  pointing 
  to 
  the 
  conclusion 
  

   that 
  the 
  pro-oestrum 
  and 
  oestrus 
  are 
  produced 
  by 
  substances 
  

   circulating 
  in 
  the 
  blood, 
  though 
  not 
  necessarily 
  secreted 
  by 
  

   the 
  ovary. 
  Kehrer 
  states 
  that 
  the 
  milk 
  from 
  a 
  suckling 
  sow 
  

   is 
  affected 
  at 
  the 
  " 
  brunst 
  " 
  period, 
  the 
  young, 
  as 
  a 
  conse- 
  

   quence, 
  developing 
  unhealthy 
  symptoms 
  ; 
  while 
  similar 
  

   phenomena 
  have 
  been 
  noted 
  in 
  the 
  case 
  of 
  suckling 
  women 
  

   during 
  menstruation 
  (Halban, 
  1901). 
  Youatt 
  (1835) 
  says 
  

   oestrus 
  can 
  be 
  induced 
  in 
  cows 
  by 
  giving 
  them 
  milk 
  obtained 
  

   from 
  other 
  cows 
  which 
  are 
  '' 
  on 
  heat." 
  

  

  The 
  statements 
  of 
  Ferre 
  and 
  Bestion 
  (Dixon, 
  1901) 
  that 
  

   injections 
  of 
  ovarian 
  extract 
  may 
  produce 
  genital 
  excitement 
  

   have 
  perhaps 
  more 
  direct 
  bearing 
  on 
  this 
  question, 
  but 
  these 
  

   observations 
  have 
  not 
  so 
  far 
  been 
  confirmed. 
  

  

  Although 
  I 
  am 
  unable, 
  for 
  the 
  reasons 
  stated 
  above, 
  to 
  

   agree 
  with 
  Fraenkel 
  that 
  menstruation 
  is 
  induced 
  by 
  the 
  

   secretory 
  activity 
  of 
  the 
  corpus 
  luteum, 
  his 
  experiments, 
  

   carried 
  on 
  in 
  collaboration 
  with 
  Cohn 
  (1901, 
  1903), 
  appear 
  to 
  

   me 
  to 
  go 
  a 
  long 
  way 
  towards 
  establishing 
  the 
  view 
  of 
  these 
  

   investigators 
  regarding 
  the 
  nature 
  of 
  the 
  connection 
  between 
  

   the 
  existence 
  of 
  the 
  corpus 
  luteum 
  and 
  the 
  chang-es 
  takinsr 
  

   place 
  in 
  the 
  uterus 
  during 
  gestation. 
  The 
  late 
  Gustav 
  Born 
  

   had 
  suggested 
  that 
  the 
  corpus 
  luteum 
  was 
  an 
  organ, 
  the 
  

   function 
  of 
  which 
  was 
  to 
  secrete 
  into 
  the 
  blood 
  substances 
  

   which 
  prepared 
  the 
  uterus 
  for 
  the 
  attachment 
  and 
  growth 
  of 
  

   the 
  embryo; 
  and 
  the 
  investigations 
  of 
  Fraeukel 
  and 
  Cohn 
  

   were 
  undertaken 
  to 
  test 
  this 
  view, 
  to 
  which 
  they 
  lend 
  support. 
  

   The 
  corpora 
  lutea 
  of 
  mbbits 
  were 
  destroyed 
  by 
  a 
  galvano- 
  

   caustic 
  needle, 
  when 
  it 
  was 
  found 
  that 
  pregnancy 
  did 
  not 
  

   continue 
  unless 
  at 
  least 
  one 
  corpus 
  luteum 
  was 
  allowed 
  to 
  

   remain. 
  Thus 
  the 
  occurrence 
  of 
  pregnancy 
  was 
  shown 
  to 
  

   depend 
  upon 
  the 
  existence 
  of 
  one 
  or 
  more 
  corpora 
  lutea 
  in 
  

   the 
  ovary. 
  

  

  VOL. 
  48, 
  PART 
  2. 
  NEW 
  SERIES. 
  24 
  

  

  