The largest drawing is a typical fusion of life study and dissection drawing – the leg is presented as standing, but the muscles are differentiated to a degree that can only be seen if the skin is stripped away. At centre right is a diagram of three ribs, with the intercostal muscles arranged crossways for greater strength. Below is a sketch of the muscles between the metatarsals of the foot, which Leonardo may have believed functioned in the same way as the intercostals. Dissection of the foot is difficult, as it contains the toughest connective tissues found within the body. But Leonardo found its compact anatomy fascinating, and he devoted considerable effort to understanding its structure. Here we see a number of sketches from different angles as Leonardo progressively removed the muscles of the sole; the scratching out and redrawing at upper right shows him struggling to make sense of his dissection notes.