© Dr Richard Wellings, Warwick Medical School, West Midlands Surgical Training Centre, UHCW Trust, 2013

Above is a computer-generated model of the muscles and bones of the right shoulder and chest. It was assembled through computed tomography (CT), a technique that uses X-rays to image slices as thin as 1 mm.

CT scanning maps the relative densities of the body’s tissues, and here the shape and position of the muscles and even the veins are clearly visible.

Such models are used to teach students and to plan operations, for they are specific to the anatomy of individual patients. They can be turned around at will, and give a better sense of the three-dimensional reality of a structure than a series of two-dimensional images. It was this sense of continuous motion that Leonardo was aiming at in his sequence of studies shown below.

These sheets comprise a sequence of eight drawings in which Leonardo turns a body through 180 degrees. The animation above captures this sequence.

All the superficial muscles of the upper arm and shoulder can be identified. There are a few idiosyncrasies (such as the division of the deltoid muscle, over the shoulder, into distinct elements), but the drawings and notes reveal a profound understanding of the muscles.

The lucidity of Leonardo’s presentation is unparalleled: medical illustration has never produced images to surpass these.