78  The  Physiology  of  Stock-Breeding. 
the  uterus  be  removed,  whether  before  or  after  puberty,  it  has 
no  effect  upon  the  development  or  functional  activity  of  the 
ovaries,  although  it  is  obvious  that  under  such  a,  condition 
pregnancy  can  no  longer  occur. 
Furthermore,  heat  cannot  be  experienced  after  complete 
ovariotomy,  the  oestrous  cycle  thereby  ceasing.  In  those  cases 
in  which  oestrus  is  reported  to  have  taken  place  after  the 
extirpation  of  the  ovaries,  its  occurrence  is  probably  to  be 
explained  by  supposing  that  a portion  of  one  of  the  ovaries 
was  accidentally  left  behind  at  the  time  of  the  operation. 
Experiments  have  shown  that  in  rabbits  and  other  animals,  a 
small  fragment  of  ovary  may  regenerate  into  one  of  quite 
considerable  size  in  the  course  of  a few  months,  and  that  after 
the  removal  of  one  ovary  the  remaining  one  can  undergo  a 
process  of  compensatory  growth.  It  is  clear,  therefore,  that 
the  power  of  functional  restitution  pos.^essed  by  these  organs 
is  by  no  means  slight.  Moreover,  there  are  cases  on  record 
of  the  occurrence  of  pregnancy  after  the  supposed  removal 
of  the  ovaries,  thus  showing  that  the  operation  had  been 
incomplete,  and  that  regeneration  had  followed. 
The  removal  of  the  uterus  and  oviducts  (f.e.,  the  tubes 
which  convey  the  ova  to  the  uterus)  does  not  pi'event  the 
occurrence  of  heat,  but  in  some  cases  the  indications  of 
pro-oestrum  are  less  marked,  since  there  can  be  no  uterine 
bleeding.  Our  experiments  have  shown  however  that  subse- 
quent to  the  removal  of  the  uterus  from  rabbits  during  early 
life,  the  animals  experienced  sexual  desire  after  reaching 
maturity,  and  copulated  normally,  and  that  the  follicles  in  the 
ovary  were  discharged  at  such  times,  ova  being  simply  expelled 
into  the  body  cavity. 
Ovariotomy,  like  castration  in  the  male,  frequently  results  in 
a deposition  of  fat  in  various  parts  of  the  body,  but  whether 
this  is  a direct  consequence  of  the  removal  of  the  generative 
organs  upon  the  metabolism,  or  an  indirect  result  due  to  the 
increased  lethargy  of  disposition  which  so  often  follows  the 
operation,  is  still  an  open  question.  Hobday*  has  shown  that 
ovariotomy  may  be  a useful  expedient  for  unworkable  or  trouble- 
some mares,  and  that  vice  may  thereby  be  cured,  especially 
where  it  is  associated  with  a prolongation  or  too  frequent 
recurrence  of  oestrus.  With  young  sows,  in  certain  localities, 
it  is  a regular  practice  to  remove  the  ovaries  to  prevent  heat  and 
to  assist  the  animals  to  fatten.  I am  informed  that  it  is  also 
common  to  remove  the  uterus  for  the  same  purpose,  but  this 
operation  is  superfluous,  since  extirpation  of  that  organ,  although 
sufficient  to  induce  sterility,  does  not  inhibit  pro-oestrum  and 
* Hobday  : On  Ovariotomy  in  Troublesome  Mares,”  Vetermary  Jour., 
Vol.  62,  1906. 
