The vesicula umbilicalis may still be distinguished in the second month as a small vesicle, not larger than a pea, near the insertion of the cord, at the navel, and external to the amnion. From the trunk, which is almost entirely occupied by the abdominal cavity, arises a short thick umbilical cord, in which some of the convolutions of the intestines may still be traced. Besides these it usually contains, as already observed, the two umbilical arteries and the umbilical vein, the urachus, the vasa omphalo-meseraica, or vein and artery of the vesicula umbilicalis, and perhaps, even at this period, the duct of communication between the intestinal canal and vesicula umbilicalis, the foetal extremity of which, according to Professor Oken's views, forms the processus vermiformis. [Illustration: _Diagram of the foetus and membranes about the sixth week._ _a_ Chorion. _b_ The larger absorbent extremities, the site of the placenta. _c_ Allantois. _d_ Amnion. _e_ Urachus. _é_ Bladder. _f_ Vesicula umbilicalis. _g_ Communicating canal between the vesicula umbilicalis and intestine. _h_ Vena umbilicalis. _i i_ Arteriæ umbilicales. _l_ Vena omphalo-meseraica. _k_ Arteria omphalo-meseraica. _n_ Heart. _o_ Rudiment of superior extremity. _p_ Rudiment of lower extremity. _From Carus._] The hands seem to be fixed to the shoulders without arms, and the feet to adhere to the ossa illi; the liver seems to fill the whole abdomen; the ossa innominata, the ribs, and scapulæ are cartilaginous. In a short time the little stump-like prominences of the extremities become longer, and are now divided into two parts, the superior into the hand and the fore arm, the inferior into the foot and leg; in one or two weeks later, the arms and thighs are visible. These parts of the extremities which are formed later than the others, are at first smaller, but as they are gradually developed they become larger. When the limbs begin to separate into an upper and lower part, their extremities become rounder and broader, and divided into the fingers and toes, which at first are disproportionately thick, and until the end of the third month are connected by a membranous substance analogous to the webbed feet of water birds; this membrane gradually disappears, beginning at the extremities of the fingers and toes, and continuing the division up to their insertion. The external parts of generation, the nose, ears, and mouth appear after the development of the extremities. The insertion of the umbilical cord changes its situation to a certain degree; instead of being nearly at the inferior extremity of the foetus as at first, it is now situated higher up on the anterior surface of the abdomen. The comparative distance between the umbilicus and pubis continues to increase, not only to the full period of gestation, when it occupies the middle point of the length of the child's body, as pointed out by Chaussier, but even to the age of puberty,