Direction of the passage of the Pelvis.—In most of the lower animals the passage of the Pelvis is straight, and on a line with the body, the two straits being opposite each other, which makes delivery much more easy with them. Even in the negroes, and other inferior races, the passage is much straighter than in the whites. The more perfect the organization therefore, the more difficult is parturition; and the more imperfect or simple the organization, the more easy is parturition. The dotted line in Plate XI. shows the direction of the passage of the Pelvis, in the human female, to be a curve, so that the child has to move, during its passage, in a circle.
PLATE XI.
The axis, or direction, of the upper strait is denoted by the line A, that of the lower strait by the line B, and that of the Vulva by the line C. The force of expulsion tending to push the child in each direction, it has to traverse a path intermediate with them all, or compounded of them all, not being able to move in either alone. This aggregate direction is denoted by the dotted curved line, which shows the direction in which the child passes, and in which the hand must be passed when introduced.
I is the Perineum.—The dotted line which crosses A denotes the upper strait, and the line I the lower strait.
CHAPTER III.
FUNCTIONS OF THE PRINCIPAL FEMALE ORGANS.
The great object for which the whole of the Female organs perform their several functions is, that of bringing into existence a new being! For this purpose they act both separately and conjointly, each one having its specific part to play in the grand phenomenon. As already remarked, it would not be in place here to give all the details of this wonderful event, but merely such a description of its principal stages, as will suffice for an understanding of the main subject of the present treatise. I shall therefore, first give the uses of the principal organs separately, and then explain the processes of conception, and fœtal development.