354 SNAKE 1n a HORSE’s EYE. 
among the antients; and amongft the moderns by Mal 
phigi, De Graaf, and above all others by the beforementi- 
ened renowned Harvey, phyfician to king Charles the 
firft of England, (the difcoverer of the true circulation of 
the blood) this induction feems to be eftablifhed upon an 
induction of facts and experiments, carrying with them 
the force of conviction, fo far as that induétion reaches. 
The only room which fome fuppofe there may be for 
doubt of the univerfality of the propofition is, that a vari-+ 
ety of animals have been found, at different times, to exift 
in the bodies of other animals, and in extraordinary pla- 
ces, which neither the difcoverers of thofe animals, nor 
others have been able to trace, with clearnefs and certain- 
ty, to what mankind, in general, can deem a probable or 
fatisfactory origin. Whether it be owing to an impati- 
ence to arrive at fome conclufion, which can ill brook the 
difficulties of the inquiry, or to the rarenefs of the cafes 
falling under the notice of perfons capable of making a 
thorough inveftigation, and the tedious progrefs of expe- 
rimental knowledge; or whether it is that we are apt to: 
fuppofe the fubje&t does not admit of mathematical certain- 
ty from the light of philofophy, I know not; but fome 
men have had recourfe to the doctrine of equivocal gene- 
ration, to account for thofe productions, as Ariftotle and 
his followers had, in other cafes, to certain occult quali- 
ties; a term by which they have endeavoured to conceal 
their ignorance of what they could not explain, but were 
unwilling to confefs. Nor are there wanting, in the pre- 
. fent day, many perfons, who will fooner deny the teftimo- 
ny of their fenfes, than allow the exiftence of an animal 
production, which they know not how to account for. 
This I fuppofe to proceed from a falfe pride, or an appre= 
henfion of being deemed credulous in a philofophic and en- 
lightened age; and becaufe, in times of ignorance, the 
paffions of illiterate men were wrought upon by fictions to 
believe in prodigies, whereby they were led blindfold, into 
opinions 
