Studies of the thorax and diaphragm of an ox, with notes; a note on the colour of smoke; a sketch of military architecture.

This elegant page continues the studies of the ox seen on RCIN 919108. Leonardo used the same pale ink as on that sheet for his initial notes and drawings, and then painstakingly went over many of them with a darker ink – this is particularly visible in the longest column of notes, where he skipped over those words that he had cancelled. The drawings also clarify many of the studies on earlier sheets, and while one might therefore expect that the page was to some degree a final expression of Leonardo’s studies of the movement of the chest, many of the notes are questions rather than statements: ‘What shape have the lobes situated between the diaphragm and the rest of the chest’; ‘How the lateral muscles of the diaphragm are the cause of movement of the lung, and of the stomach and other intestines’; ‘How the tendons of the neck raise the whole front part of the rib-cage by voluntary movement’, and so on.

At upper centre is a schematic view of the diaphragm separating the ‘receptacle of the spiritual organs’ (thorax) from the ‘receptacle of the material organs’ (abdomen). The drawing at the centre of the sheet essentially repeats that at the centre of 919108, with the vessels more clearly shown. Below is a series of four details of the chest wall: to the right, the intercostal vessels and nerve; at the centre, two views of the insertion of the muscles of the diaphragm on the ribs, with the diaphragm peeled apart into four layers – a thoracic membrane, the musculo-tendinous component of the diaphragm proper, and two abdominal membranes (as also shown in the cross-section at top left); and at bottom left of the sheet, a view of the diaphragm in place on the ribs and pierced by the oesophagus.

At the centre of the left margin is a complex image that includes a view into the abdominal cavity with the kidneys placed either side of the spine; the diaphragm partly inserting on the ribs and partly in cross-section, to show the slight bellies of its component muscles and its membranous layers; and a view into the thoracic cavity with the lungs and heart excised.

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