This magnificent series of drawings of the human skeleton, all from around 1510, shows Leonardo at his observational and analytical peak. His drawings have yet to be bettered by any modern anatomical artist, having not only
accuracy but also some impression of the spatial depth of the bone structure and its texture. Leonardo intended to show the body in all aspects from infancy to old age.
The positions of the spine with its curves, the tilt of the sacrum, and how they relate to the statics of the erect posture are correct to the last detail. Nobody before Leonardo had drawn the human skeleton so accurately nor so beautifully; most of his predecessors' work was crude by comparison. His notes on this page speak of his interest in the 'part in man, which, as he grows fatter, never gains flesh ... And among the parts which grow fat which is that which grows fattest'.
There are some anomalies in Leonardo's details of the ribcage because contemporary knowledge of the subject was not accurate, but it is noticeable that he often shows what is actually there when a more traditional illustration is wrong. Slight mistakes can be understood because of the difficulty of assembling a complete skeleton.