A nurse's handbook of obstetrics . through the lungs in vessels that lie closely in contact with theair-spaces. This process, by which waste products and oxygencan pass from fetal to maternal blood, and vice versa, throughthe walls of the vessels without any actual mingling of the bloodcurrents, is called osmosis. The placenta and foetus are connected by means of the funis,or umbilical cord, usually about twenty inches in length and thesize of the forefinger. It leaves the placenta at about its centreand enters the abdominal wall of the foetus at a point called theumbilicus, or navel, a trifle
A nurse's handbook of obstetrics . through the lungs in vessels that lie closely in contact with theair-spaces. This process, by which waste products and oxygencan pass from fetal to maternal blood, and vice versa, throughthe walls of the vessels without any actual mingling of the bloodcurrents, is called osmosis. The placenta and foetus are connected by means of the funis,or umbilical cord, usually about twenty inches in length and thesize of the forefinger. It leaves the placenta at about its centreand enters the abdominal wall of the foetus at a point called theumbilicus, or navel, a trifle below the middle of the medianline in front. The placenta is formed during the second month of gesta-tion, but is not fully developed until the third month, after whichit steadily increases in size as pregnancy advances. The umbilical cord is formed about the fourth week, and,like the placenta, increases in size with the advancement ofpregnancy. It is made up of two arteries and one large vein, 54 A NURSES HANDBOOK OF Fig. 22.—Maternal surface of the placenta. (Garrigues.) THE FCETUS. 55 which are twisted upon each other, and these are protected bya soft, transparent, bluish-white, gelatinous substance called Whartons jelly. During the early months of pregnancy the foetus, or em-bryo, as it is usually called, bears no resemblance whateverto the human form. At the end of four weeks the ovum () is merely a spongy-looking sphere containing a small,curved, gelatinous mass, with no evidence of head or extremities(Fig. 24), and if an abortion occurs at this time it is almostinvariably lost in the discharge of blood. By the end of the third month it has increased considerablyin size, being about four inches in length and weighing about
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