[Illustration: Fig. 19. THE ANATOMY OF THE EYE From G. Reisch, _Margarita philosophiae_, Leipzig,? 1503. Showing the seven tunics and three humours of the eye according to the doctrines of Renaissance anatomists.[196]] A great deal of attention was paid by the Arabians to the diseases and the structure of the eye, and the essentials of Manfredi’s description are to be found in Rhazes, Hunain ben Ishak, and Haly Abbas. The tradition presented by these writers passed early into Western science, and is reproduced, for example, in the works of Constantine Africanus and in the well-known anatomy to which the name of Richardus Anglicus (Richard of Wendover) has become attached[197] (cp. Fig. 19). Avicenna’s description of the eye is somewhat different, and gave rise to the tradition reproduced in the works of John of Peckham and of Roger Bacon (Plate XXXVIII _a_), and it influenced the views of Leonardo and even perhaps of Vesalius (Fig. 20). The views on the anatomy of the eye expressed by Rhazes, Hunain ben Ishak, and Haly Abbas were, on the whole, more widely accepted than those of Avicenna. [Illustration: Fig. 20. THE ANATOMY OF THE EYE From Vesalius, _De humani corporis fabrica_, Basel, 1543, p. 643. A, Crystalline humour; O, Albugineous humour; C, Vitreous humour; N, Cornea; Q, Conjunctiva; M, Sclerotica; G, Secundina; H, Uvea; K, Arachnoidea; E, Retina.] The treatment of the eye was always felt to be hardly within the range of the ordinary practitioner of surgery, and its structure, as we learn from Guy de Chauliac,[198] was not usually treated in the general course of anatomy. The custom was rather to refer the student to special works such as those of Jesu Aly or of Alcoatim. Manfredi’s description of the anatomy of the eye is that generally accepted at the end of the fifteenth and the beginning of the sixteenth centuries, and is unusually clear for its date. It represents a considerable advance on such writers as Henri de Mondeville (1260-1320)[199] or the pseudo Richardus Anglicus, and is far superior to the descriptions of the eye dating from the fourteenth and fifteenth centuries recently brought to light by Sudhoff.[200] We reproduce as illustrating Manfredi a diagram taken from the _Margarita philosophica_ of Gregorius Reisch (died 1525). This represents the earliest printed figure of any value of the anatomy of the eye (Fig. 19).[201] We give for comparison the figure from a thirteenth-century MS. of Roger Bacon (Plate XXXVIII _a_), representing the rival tradition of Avicenna and Alhazen that influenced Leonardo da Vinci and other contemporaries of Manfredi. These figures may be compared with that of Vesalius (1543, Fig. 20), whose description of the eye is less free from traditional bias than are most parts of his epoch-making work.