Mary Dennett 
Sex Side of Life / An Explanation for Young People 

The author’s introduction: "In reading several dozen books on sex matters for the young with a view to selecting the best for my own children, I found none that I was willing to put into their hands, without first guarding them against what I considered very misleading and harmful impressions, which they would otherwise be sure to acquire in reading them. That is the excuse for this article. It is far more specific than most sex information written for young people. I believe we owe it to children to be specific if we talk about the subject at all. From a careful observation of youthful curiosity and a very vivid recollection of my own childhood, I have tried to explain frankly the points about which there is the greatest inquiry. These points are not frankly or clearly explained in most sex literature. They are avoided, partly from embarrassment, but more, apparently, because those who have undertaken to instruct the children are not really clear in their own minds as to the proper status of the sex relation." (Excerpt from Google)