VISCERA OF THE ABDOMEN.
At an early period of uterine life, and sometimes at the period of birth, as Dr. Wilson observed in the imperfectly-developed fetus, two minute fibrous threads may be seen passing from the umbilicus to the mesentery. These are the remains of the omphalo-mesenteric vessels.
The omphalo-mesenteric are the first-developed vessels of the germ; they ramify upon the vesicula umbilicalis, or yolk-bag, and supply the newly-formed alimentary canal of the embryo. From them, as from a center, the general circulating system is produced. After the establishment of the placental circulation they cease to carry blood, and dwindle to the size of mere threads, which may be easily demonstrated in the early periods of uterine life; but are completely removed, excepting under peculiar circumstances, at a later period.
The stomach is of small size, and the great extremity but little developed. It is also more vertical in direction the earlier it is examined, a position that would seem due to the enormous magnitude of the liver, and particularly of its left lobe.
The appendix vermiformis cæci is long and of large size, and is continued directly from the central part of the cul-de-sac of the cæcum, of which it appears to be a constricted continuation. This is the character of the appendix cæci in the higher quadrumana.
The large intestines are filled with a dark-green, viscous secretion, called meconium, from its resemblance to the inspissated juice of the poppy.
The pancreas is comparatively larger in the fetus than in the adult.
The spleen is comparatively smaller in the fetus than in the adult.