WITH respect to the _Variety_, as well as the _Veracity_ of this _SUBJECT_, that I may make short Work on’t, I refer the _Curious Reader_ to the WORKS of _Jacobus Ruffius_, _Cornelius Gamma_, &c. who have not only described at large, the various _Shapes_ and _Figures_ of the most remarkable _MONSTERS_ which have been Born, but also particularly noted the _Times_ and _Places_ of their _BIRTHS_; which they have authentically collected from many creditable _Authors_. IN the small Conversation, by the _By_, which I have had either at Home or Abroad with the _Learned_, I have met with none who have deny’d the _Truth_ of this _POSITION_ in _general_; tho’ some of my _Superiors_ in this Place, have been pleas’d to contradict in _particular_, what I am just now going (and chiefly for that very reason) about to publish to the World, in the next following _Chapter_. BUT notwithstanding that we all agree as to the _FACT_, yet I have found but few ready to discuss the proper _Causes_ of _Monstrous BIRTHS_: Only so far, that _some_ would have them to proceed immediately from the Commixture of _Humane_ with _Brutal SEED_; _others_, directly from the _INFLUX_ of the _Stars_; _Some_ again, from a vitious _Constitution_, or oblique _Situation_ of the _WOMB_; others also, from a _Lascivious_ and enormous _Act_ of _Copulation_; and _some_ at last, from the sordid and corrupted _SEMINAL Matter_ of the _Persons Copulating_. Which may be all indeed, in some respect, consentaneous to _Reason_; but notwithstanding, in speaking to such _Causes_, I think, we ought previously to consider the _Requisites_ concurring to the _Production_ of the FOETUS; what they naturally are, and how they ought to be _qualify’d_. THE FIRST and chief of which is the _Forming Faculty_; 2ly. The _two Instruments_, by which this _Faculty_ operates, _viz._ the _SPIRIT_ or innate _Seminal Heat_, and the _Imagination_, 3ly. _The MATTER_, viz. both the _SEEDS_, and the _Menstruous Blood_; 4ly. And lastly, the _PLACE_, namely the WOMB: Whence I conclude that any _one_, or _more_, or (perhaps) all of _THESE_, degenerating from their _due state_ or _natural Qualities_, may prove the _Cause_ or _Causes_ of a _MONSTROUS CONCEPTION_, or _Æquivocal GENERATION_.