The more we know of the facts of sex, the right and normal part sex activities play in life, and all that tends to abuse and degrade them, the better able we will be to make sex a factor for happiness in our own lives and that of our descendants. Mankind, for its own general good, must desire that reproduction--the real purpose of every sexual function--occur in such a way as to perpetuate its own best physical and mental qualities.
It is a universal rule of physical life that every individual being undergoes a development which we know as its individual life and which, so far as its physical substance is concerned, ends with death. Death is the destruction of the greater part of this individual organism which, when death ensues, once more becomes lifeless matter. Only small portions of this matter, the germ cells, continue to live under certain conditions which nature has fixed.
The germ cell--as has been established by the microscope--is the tiny cell which in the lowest living organisms as well as in man himself, forms the unit of physical development. Yet even this tiny cell is already a highly organized and perfected thing. It is composed of the most widely differing elements which, taken together, form the so-called protoplasm or cellular substance. And for all life established in nature the cell remains the constant and unchanging form element. It comprises the cell-protoplasm and a nucleus imbedded in it whose substance is known as the nucleoplasm. The nucleus is the more important of the two and, so to say, governs the life of the cell-protoplasm.
The lower one-celled organisms in nature increase by division, just as do the individual cells of a more highly organized, many-celled order of living beings. And in all cases, though death or destruction of the cells is synonymous with the death or destruction of the living organism, the latter in most cases already has recreated itself by reproduction.
We will not go into the very complicated details of the actual process of the growth and division of the protoplasmic cells. It is enough to say that in the case of living creatures provided with more complicated organisms, such as the higher plants, animals and man, the little cell units divide and grow as they do in the case of the lower organisms. The fact is one which shows the intimate inner relationship of all living beings.