The length of a full-grown foetus is generally about eighteen or nineteen inches; its weight between six and seven pounds. The different parts are well developed and rounded; the body is generally covered with the vernix caseosa;[28] the nails are horny, and project beyond the tips of the fingers, which is not the case with the toes; the head has attained its proper size and hardness; the ears have the firmness of cartilage; the scrotum is rugous, not peculiarly red, and usually containing the testes. In female children the nymphæ are generally covered entirely by the labia, the breasts project, and in both sexes frequently contain a milky fluid. As soon as a child is born, which has been carried the full time, it usually cries loudly, opens its eyes, and moves its arms and legs briskly; it soon passes urine and fæces, and greedily takes the nipple. (Naegelé's _Hebammenbuch_.) Thus, then, in the space of forty weeks, or ten lunar months, from an inappreciable point, the foetus attains a medium length of about eighteen or nineteen inches, and a medium weight of between six and seven pounds. As these observations on the development of the ovum show that the structural arrangement of the embryo undergoes a succession of changes, by which it gradually rises from the lowest to the highest scale of formation, so we shall find it furnished with a succession of means for its nutrition, each corresponding more or less to the particular grade of development which it may have attained. Its earliest source of nourishment is doubtless the vitellus, or albuminous contents of the vesicula umbilicalis. The radicle or primitive trace, in this respect, bears a strong analogy to the seed of a plant; it brings with it its own supply of nourishment for its first stage of growth; in the latter, the cotyledons afford nourishment to the little plumula, until, by the formation of roots and absorption of moisture from the surrounding soil, it is enabled to support the early rudiment of the future plant. The early function of the chorion is very analogous to that of roots; it is an absorbing apparatus, collecting nourishment by means of its numerous absorbing fibrillæ: hence, according to Lobstein, the umbilical vein exists for some time previous to the umbilical arteries, and seems to perform an office in the foetus similar to that of the thoracic duct at a later period; its radicles or absorbing extremities seem to absorb a milky fluid, which after the first two months is found in the placenta, and which must be looked upon as a means of nourishment which does not exist in the latter months. This milky fluid was noticed by Leroux, who even then expressed his doubts, whether the radicles of the umbilical vein receive blood from the mother, or whether they only serve to absorb a white fluid which resembles chyle. In some manuscript notes of Dr. Young's lectures, which were taken by the late Dr. Parry, of Bath, when a student at Edinburgh, we find the