_But what has given me much more trouble, in this Work, than if I had written it in Latin, is the embarrassment of expressing images, of which the terms and descriptions are declared indecent by use. A dispensation, however, from a due attention to these scruples would have been very disagreeable to my own disposition, with which I could never have reconciled any labor at the expence of what I pride myself on, a due regard for the laws of decency. Yet to this duty it is that are owing the great difficulties that stopped me at every step. I dare aver, then, that I have neglected no precaution for giving to this Work all the modesty in the expressions that the subject would admit. There are, indeed, certain objectionable images inseparable from this matter; but how could I avoid them? Was it fit for me, on such important objects, to keep silence? Doubtless not. The sacred Authors, the Fathers of the Church, who almost all wrote in living languages; the Theological Writers, have not thought themselves obliged to pass over in silence the crimes of obscenity, because they could not be pointed out without naming them, without words, in short. I judged myself authorised to follow their example, and I dare say, with St. AUGUSTIN, “If what I have written scandalizes any vitious persons, let them rather blame their own turpitude than the words which I have been obliged to make use of, for explaining my thoughts on the act of generation in mankind. I hope that the truly modest and virtuous reader will easily forgive the expressions which I have been forced to employ.” I will add to what this great Divine says, that I hope to merit the grateful acknowledgment and approbation of the moral and the sensible, who know the general proneness of the world to wicked practices, and who will approve, if not my success, at least the intention of my undertaking._ _I have not in this, no more than in my first edition, touched upon the moral part, and that for HORACE’s reason_, ——Quod medicorum est Promittunt Medici——