258 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1787« 



and that, if one ovarium is removed, the other will be called on by the constitu- 

 tion to perform the operations of both ; by which means the animal should pro- 

 duce, with I ovarium, the same number of young as would have been produced 

 if both had remained. 



With an intention to ascertain these points, as far as I could, I was led to 

 make the following experiment ; and for that purpose chose pigs in preference to 

 any other animal, because they are easily managed, and breed perfectly well 

 under the confinement necessary for experiments. Having selected 1 female 

 ones of the same colour and size, and likewise a boar pig, all of the same 

 farrow ; after having removed one ovarium only from one of the females, and 

 cut a slit in one of its ears, that there might be no mistake between it and the 

 other, I had them well fed and kept warm, that there might be no impediment 

 to their breeding ; and whenever they farrowed, their pigs were taken away 

 exactly at the same age. 



About the beginning of the year 1779> they both took the boar ; but the one 

 which had been spayed earlier than the perfect female. The distance of time 

 however was not great, and they continued breeding at nearly the same times. 

 The spayed animal continued to breed till Sept. 1783, when she was years 

 old, which was a space of more than 4 years. In that time she had 8 farrows ; 

 but did not take the boar afterwards, and had in all jQ pigs. The perfect one 

 continued breeding till December 1785, when she was about 8 years old, a 

 period of almost 6 years, in which time she had 13 farrows, and had in all 1 62 

 pigs; after this time she did not breed: I kept her till Nev. 1786. 



I have here annexed a table of the different times of each farrow, with the 

 number of pigs produced. 



Farrows. 



1 . 



2 . 



3 '. 



4 . 



5 . 



6 . 



7 . 



8 . 



■ Spayed Sow. 



Number of young. 



... 6 



8 

 6 



10 

 10 



9 



14 

 13 



Te 



Time. 



Dec. 1779 



July 1780 



Jan. 1781 



Aug. 1781 



Mar. 1782 



Sept. 1782 



May 1783 



Sept. 1783 



Farrows. 



1 .. 



2 .. 



3 ., 



Perfect Sow. 



Number of young. 



... 9 



Time. 



Dec. 1781 



June 1782 



Dec. 1782 



June 1783 



Oct. 1783 



November following she was put 

 to the boar, but brought no pigs. 

 April 1784, she was again put to the 

 boar, without effect, and never was 

 observed to take the boar afterwards, 

 though often with him. November 

 1784, she was killed. 



6 

 8 

 13 

 10 

 16" 

 13 

 12 



87 



Eleven pigs more than were pro- 

 duced by the spayed sow in her eight 

 farrows. The remainder of her far- 

 rows as follow : 



