MOST errors arise not from absolute ignorance but from an inexact conception of just those things which one thinks one knows best. This is especially true in the sphere of.
The simplest and clearest possible presentation of the underlying physical phenomena should therefore always be given first.
The physical foundation and starting point of our whole life, with all its weal and woe, with all its profound agitations and emotions, are to be found in two minute organs, two small tumours, which in the adult body furnish the reproductive cells. These are, as everyone knows, in the male the two testes or testicles, hard and round, as big as a finger-joint, which produce the sperm-cells; in the female the two ovaries, in shape and size like a dried plum, which furnish the egg-cells.
These two types of organs are often grouped together under the name of Gonads, or Glands.
It is essentially the testes or the ovaries, as the case may be which determine the difference, because they produce the reproductive cells and also because of the specific chemical constituents which they pour into the blood stream.
The most extraordinary thing about the testicles is that they migrate from the abdominal cavity where they are developed, in order to form a special outgrowth at the bottom of the belly. The testicles in man, like the ovaries in woman, are originally developed fairly high up in the abdominal cavity on either side of the lumbar vertebrae. But in the higher mammals and in man the testicles leave their original situation before birth and move lower and lower, like a hernia, forcing a passage right through the muscle fibres of the abdominal wall and pushing the peritoneum before them.