Mother, Nurse and Infant / A Manual Especially Adapted for the Guidance of Mothers and Monthly Nurses, Comprising Full Instruction in Regard To Pregnancy, Preparation for Child-birth, and the Care of Mother and Child, and Designed to Impart so Much Knowledge of Anatomy, Physiology, Midwifery, and the Proper Use of Medicines as Will Serve Intelligently to Direct the Wife, Mother and Nurse in All Emergencies.

by S. P. Sackett

The successive changes in the development were, 1st, a germ membrane visible immediately after the bursting of the vesicle; 2d, at some point an aggregation of granules forming the cumulus of the blastoderma; 3d, the embryo developed lying at this point, as it were upon the membranes, which consist of three superimposed laminæ or layers; 4th, on the serous layer arise the organs of animal life, the brain and spinal marrow, organs of sense, skin, muscles, tendons, ligaments, cartilage, and bone; on the mucous the organs of vegetative life, the intestinal canal, lungs, liver, spleen, pancreas and other glands. The heart and vascular system arise from the vascular layer (if this can be considered a separate one).

About the second week, or perhaps the third, there is a mass of globules loosely connected together forming the primitive streak of Von Baer, and around this the area vasculosa is developed. The globules of the primitive streak, seem next to be developed into two laminæ dorsales, which is the axis of the future embryo, and the origin of the spinal column. That portion of the fluid that separates the chorda dorsalis from the lamina dorsalis is the future spinal cord, and brain. Two other lamina—laminæ ventrales of Von Baer—are in the mean time proceeding from the axis of the embryo, one on each side; they grow laterally and converge below the axis.

After the rudiments of organic life have been commenced in the central portion of the serous layer, a fold of its peripheral portion arches over the dorsal surface of the embryo so as to represent a sac, and is composed of two membranes; the one next to the fœtus is the amnion, the other is gradually separated from the amnion and joins the serous lamina of the blastoderma; this is the false amnion of Pander.

The heart is formed at this early period, and although there is no septum between the ventricles, a vein may be seen entering into it, and an artery passes out which divides into four branches to be distributed and ramified in different portions of the fœtus.

The abdomen is yet an open cleft, in which (but projecting beyond it) is the heart, which is of very large dimensions; behind the heart is the liver, and under the liver the intestine which is attached by means of a distinct mesentery. At this period (three weeks) the lungs are constituted of five or six lobules, and two large glandular structures may also be discerned along the vertebral column, which are called Wolfian bodies; these anticipate the function of the kidneys. The alantois is seen arising from the lower part of the intestinal canal on a little vesicle and extending so as to encircle the embryo.

During the second month the extremities are growing, and become more projecting; the body is curved and the head bent downwards; there are indications of the nostrils and a gaping oral aperture; the forehead is more swelled because of the development of the hemispheres of the brain; the spinal cord is cylindrical of nearly uniform thickness and terminating in a blunt extremity—posteriorly it is open; the medulla oblongata makes a bend forwards at the top of the neck, and then ascends perpendicularly into the capacious cranium.

The first centres of ossification appear about the seventh week on the clavicle and lower jaw. At this time the kidneys and renal capsules begin to appear. The only trace of muscular fibre is in the diaphragm. The vertebral arches are not yet closed in, and the ribs appear like little streaks; the liver is very large and granular. The stomach is assuming somewhat of its normal form; the urinary bladder is enclosed, but the anus is imperforate. At this time the embryo is about an inch in length.

At two months the rudimentary organs of generation may be distinguished, but their development does not clearly show the sex. The embryo is from one and a half to two inches long and weighs near half an ounce, the head forming two-thirds of the whole.

After this period the different parts are developed with tolerable rapidity. At ten weeks the embryo is about two and a half inches in length. At the end of the third month it is from five to six inches long and weighs from three to four ounces. The thorax is closed at all points but is only slightly developed; the cord contains no intestines, and its spiral turns are evident; the nails are beginning to appear; the sex is distinct, and the skin acquires some consistence. At the fourth month the fœtus is six to eight inches in length, and weighs from seven to eight ounces. A fœtus born at this period might live for an hour or two. At five months the length of the body, including head and feet, is from eight to ten inches, and weighs from eight to eleven ounces; at six months the weight is about one pound, and the length is eleven to twelve and a half inches.

At seven months the fœtus is from twelve and a half to fourteen inches long and weighs from three to five pounds. The hands and feet, including the nails, are developed; all its parts are tolerably firm, and their respective dimensions better proportioned than formerly. The scrotum usually contains one or both testicles, they having descended through the inguinal ring, from their original place near the vertebral column; the eyelids are partly open; the skin is very red and covered with down. Many children live and are reared that are born at seven months.