The head is much more voluminous; and this is not a result of the extent of the face, for that is small and contracted, because the apparatus of smell and of mastication are not yet developed. Nor is the head only more voluminous; it is also more active, and forms a centre toward which is directed all the effort of life. The spine of the back has not either the minuter prominences or the general inflexions which favor the action of the extensor muscles, a circumstance which is opposed to standing perpendicularly during the first months. The infant consequently can only crawl like a quadruped. Little distinction can then be drawn, and that with difficulty, from the comparative width of the haunches, and magnitude of the pelvis. That part is scarcely more developed in the female than in the male; its general form is the same; and its different diameters have similar relations to each other. The length of the trunk is great in proportion to the limbs, which are slightly and imperfectly developed. Owing to the great length of the chest, and the imperfection of the inferior members, the middle of the body then corresponds to the region of the umbilicus. An infant having other proportions, would appear to be deprived of the characters of its age. In the locomotive system, the muscles have not yet acted with sufficient power and frequency to modify the direction of the bones, and to bestow a peculiar character upon their combination in the skeleton. The fleshy and other soft parts do not yet appear to differ from those of the male, either as to form or as to relative volume. The vital functions of digestion, of circulation and respiration, of nutrition, secretion, and excretion, are performed in the same manner. The want of nourishment is unceasingly renewed, and the movements of the pulse, and of inspiration and expiration, are rapidly performed, owing to the extreme irritability of all the organs. The mental functions present the same resemblance; the ideas, the appetites, the passions, have the greatest analogy; and similar moral dispositions prevail. Little girls, it has been observed, have in some measure the petulance of little boys, and these have in some measure the mobility and the inconstancy of little girls. Owing to the pelvis not being yet developed, little girls walk nearly like children of the other sex. These points of resemblance do not continue during a long period: the female begins to acquire a distinct physiognomy, and traits which are peculiar to her, long before we can discern any of the symptoms of puberty; and although the especial marks which distinguish her sex do not yet show themselves, the general forms which characterize it may be perceived. These differences, however, are only slight modifications, more easily felt than determined.