The First Part

There is no significant difference in proportion between children of three years, whether male or female, except that girls have slightly narrower shoulders, a more pointed and larger belly, and are slightly wider at the hips. Their small limbs are somewhat softer, and their backs are more even. This is the only difference I have been able to notice between the two sexes.

Between children, whether boys or girls of three years, hardly any difference in their postures is observed. Except that girls have narrower shoulders and thicker, more rounded bellies, and are broader at the hips and softer in their limbs, as well as having smoother backs, depending on whether they are lean or stout. This is the only distinction I have noticed.

There is little difference between male or female children aged two to three years, except that girls have slightly narrower shoulders, a slightly larger and elevated belly, and somewhat broader hips and softer limbs, and their backs are smoother. This varies depending on whether they are thin or plump. This is the difference I have been able to observe.

Among children, boys or girls of three years, there is hardly any difference, except that girls have slightly narrower shoulders and a somewhat elevated and thicker stomach, broader hips, and softer limbs on the back. This is the distinction I have been able to notice.

Translation Notes

Settling: In this context, it refers to the posture or physical disposition.
Limbs: This might denote softer in terms of muscle or skin texture, not weaker.
Unity or Smoothness: When mentioning backs being more "unified" or smooth, it may refer to the musculature or how evenly the surface is shaped.