CHAPTER II.
PHYSIOLOGY OF THE FŒTUS.
Fœtal Development.—About two weeks after impregnation, the new organization becomes about as large as a pea, and its two envelopes, or membranous, coverings, called chorion and amnion, with a gelatinous substance inclosed between them are distinctly visible. A thin membrane is also formed over the whole internal surface of the womb, called the decidua. Soon after a small white thread-like substance appears, which is the commencement of the brain and spinal marrow; before the twentieth day the eyes are visible; and before the first month is completed a cartilaginous or grisly substance indicates the future bones, &c.
In the second month the cartilage begins to harden into bone, the rudiments of the teeth are visible, the general form is developed, and it is about an inch in length. During the third month the heart is developed, and, although without blood, has a slight degree of motion. At the end of three months, the eye-lids are distinct, the lips perfect, the fingers and toes apparent, the heart beats forcibly, and all parts are well defined, the weight being two or three ounces, and the length four or live inches. In the fourth month the muscles become distinct, the brain and spinal marrow firmer, the abdomen covered with integument; a large portion of the bony structure is ossified, the rudiments of the second set of teeth, are seen under the first, and the substance called meconium begins to collect in the bowels.
Near the middle of the fourth month, the uterus rises above the pelvis into the cavity of the abdomen, when the mother becomes remarkably sensible of the motions of the fœtus.
This period has been called quickening, upon the erroneous supposition that the fœtus then first became endowed with life; but it is truly alive from the moment of conception. Sickness at the stomach, tendency to faintness, &c, denote the disturbance occasioned by the sudden change of position.
