A folio from Leonardo's 'Anatomical Manuscript B'.

Recto: two drawings of a male torso showing the muscles of the anterior and lateral walls of the abdomen; notes on the drawings.

Verso: two drawings of the torso of a man, in profile to the right, showing superficial muscles; two small diagrams indicating muscle surface seen in profile, and represented according to ancient and modern usages. The principal drawing is again an amalgam of information obtained from both dissection and surface observation. Though only the bodies of the muscles are shown, without their origins or insertions, they are represented in a more distinct manner than may be seen in even the most heavily muscled individual. The arm has been cut away to display the muscles on the side of the torso: serratus anterior is shown as five bodies (lettered n m o p q) interdigitating with the external abdominal oblique muscle (a) to create the ‘serrated’ appearance which gives the muscle its name. The external abdominal oblique muscle is inserted into an aponeurosis (a sheet-like tendon) which covers the rectus abdominis muscle, across the front of the abdomen. The deltoid (shoulder), pectoralis major (chest) and latissimus dorsi (labelled superiore, ‘upper’) muscles are also prominent.

In the lower drawing, latissimus dorsi has been removed to show more of serratus anterior, extending backwards towards the scapula, and a vessel travelling in the depths of the axilla, possibly the middle subscapular artery. The two small sketches of curves at lower right are annotated ‘a b c [above] is the concavity of antique muscle; c d f [actually e, below] is modern’. Leonardo’s use of the words antico and moderna (rather than vecchio and giovane) suggest that he was not discussing changes of muscle shape with ageing, but differing modes of representing muscular bodies in ancient and Renaissance sculpture: he clearly believed that the muscles in ancient statues were more sharply delineated than those in modern works.

Text from M. Clayton and R. Philo, Leonardo da Vinci: Anatomist, London 2012