TOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 125 



This reasoning will probably appear not perfectly consentaneous to certain well 

 established facts on the subject of extra-uterine foetuses ; for dissection has fully 

 evinced the possibility of a foetus being perfectly evolved, and of acquiring con- 

 siderable bulk, either in the ovary, abdomen, or tube. I do not hesitate to acknow- 

 ledge the full force of these facts ; but I cannot admit that they subvert the principle 

 I wish to establish from experiment ; because I conceive there is an essential differ- 

 ence whether nature spontaneously dispenses with her usual modes, and attempts to 

 effect her ultimate purpose by irregular means ; or whether, proceeding in the or- 

 dinary course of her operations, she suffers an impediment which a physiologist may 

 have produced to thwart her designs. In the first case, she may be provided with 

 an expedient ; in the last, she will probably be left without resource. 



Here again we may notice the experiment mentioned by Nuck, which, though 

 under similar circumstances, was attended with a different result. Some who feel 

 themselves disposed to venerate his authority, will probably oppose his experiment 

 to mine, and think it incumbent on me to account satisfactorily for the difference. 

 I can by no means acknowledge such an obligation ; for to confer validity on experi- 

 ment by reasoning, is to invert the order of inquiry, and support facts by con- 

 jectures. It is sufficient for my credit to be able to adduce evidence of the truth of 

 what I advance, and for this evidence I rely on my preparations. 



The train of reasoning which I have lately pursued, led me to extend my inquiries 

 into this particular question still further ; and as in the last experiments the vesicles 

 were known to be just on the point of bursting before the tube was cut through ; 

 the next step in the inquiry appeared to be, to determine the consequences of di- 

 viding the tube a short time after the rudiments of the foetus had passed. Will the 

 procreative operations be suspended, if the tube be cut through after the ovum is 

 deposited in the uterus ? 



Exper. I repeated the operation on 2 rabbits, one of which had received the 

 male 2 days and 18 hours, the other 2 days and 12 hours. I knew from my own 

 experiments, as well as those of De Graaf, that the vesicles had discharged their 

 contents before either of these periods. The examination of these at the usual 

 time, proved that the actions of these parts suffer no interruption by a division of 

 the tube made after the rudiments of the foetus have been conveyed into the uterus; 

 for there were corporea lutea in both ovaries, and foetuses in both cornua uteri. 



These experiments I think overturn, as far as experiment can, every argument 

 which has hitherto been adduced to support the hypothesis, that the affusion of the 

 semen on the ovaries, either in a sensible form or in that of aura seminalis, is essen- 

 tial to impregnation : for if the ovaries were susceptible of their proper excitement 

 only by the contact of semen, by what accideut has it happened that the effects of 

 that excitement are not more obvious and further advanced in those experiments, 

 where nothing was done to intercept its course for 48 hours, than in those where 

 all communication between the uterus and ovary had been cut off before the means 

 for impregnation had been employed? We should expect in the one case to find the 



