192 
Dr. Haighton's experimental Inquiry 
SECTION III. 
What is the Form of that Substance which passes from the Ovaries 
in consequence of Impregnation ? 
No sooner had the researches of the physiologists retraced 
the existence of the new-born animal to the ovaries, than their 
curiosity was excited to discover the form it assumed while 
resident in these bodies, and especially at that particular 
time when the foetal primordia are about to escape from them. 
The analogous phenomena of oviparous animals, and the 
structure of the ovaries as described by De Graaf, concurred 
to favour an opinion, that in viviparous animals there existed 
ova in these bodies, and indeed from this very circumstance 
they received their name. But though several physiologists 
have concurred in this opinion, there has not been any strict 
coincidence respecting their state while in the ovary. Some 
have thought that the vesicles described by De Graaf were 
the true ova, and that these are the bodies that are expelled 
by impregnation. Others, with greater probability, have con- 
sidered these vesicles as the apparatus destined by nature, 
under the influence of the proper stimulus, to form the ovum : 
and though at all times they contain a glairy kind of fluid, 
from the stimulus of impregnation this fluid becomes a small 
vesicle or ovum seated within the larger vesicle, which now 
becoming thickened, and acquiring a yellow colour, is called 
the corpus luteum : from this body the interior vesicle or ovum 
is protruded. 
Others again refuse assent to both these opinions, and con- 
tend that the substance extruded from the corpora lutea has 
