This much did I say respecting this check in the first edition of this work. That is what I call the chemical check. The idea of destroying the fecundating property of the semen was original, if it did not originate with me. My attention was drawn to the subject by the perusal of "Moral Physiology." Such was my confidence in the chemical idea that I sat down and wrote this work in July, 1831. But the reflection that I did not know that this check would never fail, and that if it should, I might do someone an injury in recommending it, caused the manuscript to lie on hand until the following December. Some time in November I fell in with an old acquaintance, who agreeably surprised me by stating that to his personal knowledge this last check had been used as above stated. I have since conversed with a gentleman with whom I was acquainted, who stated that, being in Baltimore some few years ago, he was there informed of this check by those who have no doubt of its efficacy. From what has as yet fell under my observation, I am not warranted in drawing any conclusion. I can only say that I have never known it to fail. Such are my views on the whole subject, that it would require many instances of its reputed failure to satisfy me that such failures were not owing to an insufficient use of it. I even believe that quite cold water alone, if thoroughly used, would be sufficient. In Spallanzani's experiments warm water was unquestionably used. As the seminal animalcule are essential to impregnation, all we have to do is to change the condition of, or, if you will, to kill them; and as they are so exceedingly small and delicate, this is doubtless easily done, and hence cold water may be sufficient. What has now been advanced in this work will enable the reader to judge for himself or herself of the efficacy of the chemical or syringe check, and time will probably determine whether I am correct in this matter. I do know that those married females who have much desire to escape will not stand for the little trouble of using this check, especially when they consider that on the score of cleanliness and health alone it is worth the trouble. A great part of the time no check is necessary, and women of experience and observation, with the information conveyed by this work, will be able to judge pretty correctly when it is and when it is not. They may rest assured that none of the salts mentioned will have any deleterious effect. The sulphate of zinc is commonly known by the name of white vitriol. This, as well as alum, have been extensively used for leucorrhae. Acetate of lead would doubtless be effectual--indeed, it has proven to be so; but I do not recommend it, because I conceive it possible that a long continued use of it might impair the instinct.