114 PHILOSOPHICAL TRANSACTIONS. [ANN0 1797. 



pora lutea were more or less evident, according to the interval of time that had 

 elapsed ; I may then say that no corpora lutea exist in virgin animals, and that 

 whenever they are found, they furnish incontestable proof that impregnation either 

 does exist, or has preceded. But a proper distinction between past and existing 

 impregnation can be made only by tracing the phenomena of recent fecundation 

 progressively, and noting the appearances in the different stages. I was therefore 

 under the necessity of repeating with care several of De GraaPs experiments, that 

 I might bear testimony to the truth of them, at least so far as the results coincided 

 with my own. 



Exper. Having therefore procured several virgin rabbits in a fit state for impreg- 

 nation, I admitted one of them to the male. Twelve hours afterwards it was 

 killed, and on examining the ovaries several of the vesicles evidently projected ; 

 they had lost their transparency, and were become opaque and red. When punc- 

 tured, a fluid of the same colour escaped. I made sections through some of them ; 

 but at this early period the corpora lutea, which are formed by the thickening of the 

 parietes of the vesicles, were not very evident. I therefore determined to examine 

 them in a more advanced state. 



Exper. Another rabbit being admitted to the male, I examined it 24 hours 

 afterwards. The colour of the fluid contained in the vesicles was similar to that of 

 the last experiment. The vesicles projected more evidently, and their thickened 

 parietes manifesting the commencement of corpora lutea were become more 

 apparent. 



Exper. I inspected the ovaries of another rabbit 48 hours post coitum. At this 

 period the vesicles seemed to be in the very act of bursting, and a semi-transparent 

 substance, of a mucus-like consistence, was beginning to protrude from some of 

 them ; others indeed were less advanced. The fimbriated extremities of the fallo- 

 pian tubes were preparing to receive their contents, as appeared by having quitted 

 their usual position, and embraced the ovaries in such a degree, that only a small 

 portion could be seen till the tubes were taken away. Sections being made into the 

 thickened vesicles, the formation of corpora lutea appeared to have made further 

 advances. From the appearance of an incipient rupture of the vesicles in this ex- 

 perimentj it was but reasonable to expect that their contents would soon have es- 

 caped ; but as my views were directed to the formation of a corpus luteum, I de- 

 ferred the next examination to a more distant time. 



Exper. In 2 days and 12 hours after coition, I examined the ovaries of another 

 rabbit. The foetal rudiments had escaped ; but the cavity of the ovarian vesicles 

 had suffered but little diminution. Bristles were easily introduced by the ruptured 

 orifices. In this experiment the advances towards the formation of a perfect cor- 

 pus luteum were such as the period of examination would naturally lead us to ex- 

 pect. The contents of the vesicles having escaped, it was but reasonable now to 

 look forward to a speedy obliteration of the cavity. I therefore examined these 

 parts under similar circumstances on the 3d, 4th, and 5th day. In the last experi- 



