VOL. LXXVII.] PHILOSOPHICAL TRANSACTIONS. 25p 



Farrows. Number of young. Time. 



9 12 Feb. 1784 



10 16 June 1784 



11 12 Dec, 1784 



12 16 May 1785 



13 19 Dec. 1785 



75 



After which she bred no more. The first 8 farrows were 87, the last 5 

 farrows were 75, total 162, the number from the spayed one 76, being 86 less 

 than farrowed by the imperfect animal. 



It is observable, that both sows rather increased in their number each time 

 the older they grew, though not uniformly ; the difference between the first and 

 last in both animals being considerable. From the above table we find, that the 

 sow with only one ovarium bred till she was 6 years old, from the latter end of 

 1779 till Sept. 1783, about 4 years, and in that time brought forth 76 pigs. 

 The perfect animal bred till she was 8 years of age. In the last, if conception 

 depended on the ovaria, it was to be expected that she would bring forth double 

 the number at each birth ; or, if she did not, that she would continue breeding 

 for double the time. We indeed find her producing 10 more than double the 

 number of the imperfect animal, and continuing to breed much longer. 



From a circumstance mentioned in the course of this experiment it appears, 

 that the desire for the male continues after the power of breeding is exhausted 

 in the female ; and therefore does not altogether depend on the powers of the 

 ovaria to propagate, though we must at the same time allow, that it may be in- 

 fluenced by the existence of such parts. If these observations should be con- 

 sidered as depending on a single experiment, from which alone it is not justi- 

 fiable to draw conclusions, I have only to add, that the difference in the number 

 of pigs produced by each was greater than can be justly imputed to accident, 

 and is a circumstance certainly in favour of the universality of the principle I 

 wished to ascertain.* 



From this experiment it seems most probable, that the ovaria are from the 

 beginning destined to produce a fixed number, beyond which they cannot go, 

 though circumstances may tend to diminish that number ; that the constitution 

 at large has no power of giving to 1 ovarium the power of propagating equal to 

 2; for, in the present experiment, the animal with 1 ovarium produced 10 pigs 

 less than half the number brought forth by the pig with both ovaria. But that 

 the constitution has so far a power of influencing one ovarium, as to make it 



* It maybe thought by some, that I should have repeated this experiment; but an annual expense 

 of twenty pounds for ten years, and the necessary attention to make the experiment complete, will 

 be a sufficient reason for my not having done it. — Grig. 



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