concerning Animal Impregnation . 193 
110 vesicular appearance ; and though by some it has been 
called an ovum, yet that name is not applicable to it from any 
resemblance of figure, but rather from its agreement with an 
egg in being the substance in which the rudiments of the fu- 
ture animal are contained, 
De Graaf contended that the primordia foetus while in the 
ovary is vesicular, as appears in his work ; in which, after der 
scribing the enlargement of the proper vesicles usually con- 
nected with his name, he says, “ prasterea aliquot post coitum 
“ diebus tenuiori substantia prsediti sunt, et in sui medio 
“ limpidum liquorem membrana inclusum continent, quo una 
<e cum membrana foras propulso, exigua solum in iis capacitas 
“ superest.” He is therefore decidedly, of opinion, that as 
soon as the product of conception becomes the subject of no- 
tice, it has a vesicular form, and this he thinks takes place at 
the end of the third day, though the substance passes from 
the ovaries several hours before this time. He seems rather 
to assert, that it passes in a vesicular form, than to prove it ; 
for in fifty-two hours after the approach of the male, he found 
the ovarian vesicles were empty, though he could not now find 
the new vesicles either in the uterus or the tubes. But in se- 
venty-two hours they were so evident, that he could distin- 
guish with ease the two membranes of which they are formed, 
viz. the chorion and amnios ; so that they cannot be very 
small at this time. Hence it would follow, that if on a repeti- 
tion of this experiment on the third day no vesicles should 
happen to be found, it would not be from minuteness that 
they would escape observation ; therefore should any one be 
disposed to search for them, he need not bend his sight, as if 
looking at microscopical objects. 
MDCCXCVII. C C 
