162 Dr. Haighton’s experimental Inquiry 
have assumed the proper characters of an ovum. As soon as 
these rudiments manifest that opaque spot, or “ dim speck of 
“ entity/' which is known to evolve the foetus by regular and 
progressive steps; another stage of the inquiry then com- 
mences, viz. to trace the visible formation of the new animal 
through its whole course; but as this belongs rather to the 
oeconomy of the foetus than the mother, it is not intended to 
form any part of this paper. 
I perceive, however, that I cannot investigate the question 
of the proximate cause of impregnation in a satisfactory way 
without first determining what are the evidences or proofs that 
impregnation has taken place : this then necessarily becomes 
a preliminary question. I therefore restrict my inquiry to the 
three following subjects. 
First. What are the evidences of impregnation ? 
Second. What is the proximate cause of impregnation ? 
And, third. Under what form do the rudiments of the foetus 
pass from the ovary to the uterus ? 
SECTION I. 
What are the Evidences of Impregnation f 
The investigation of every complicated subject of inquiry 
comprehends within its range a more or less extended recital 
of facts, depending in a greater or less degree on eqch other, 
but primarily arising from some fundamental proposition. 
As this proposition is generally the basis on which this su- 
perstructure is raised, or the trunk from which the various 
ramifications of inquiry proceed, it is essential, to the establish- 
ment of the ultimate conclusions, that the antecedent question 
