'Theory of Perception', anatomical drawing, 1686.
© Science Museum / Science & Society Picture Library
Line diagram taken from the 1686 French edition of 'Tractatus De Homine' (Treatise of Man, first published in 1662) by Rene Descartes (1596-1650), showing the anatomy of the eyeball and its muscles. Treatise of Man formed part of a larger work, 'Treatise of the World', in which Descartes gives his notion of universal physics. This was not published during his lifetime due to the censure of the Catholic church. Even though details in Treatise of Man are inaccurate, the principles Descartes defined influenced the development of modern physiology.