We have said that throughout the second period, the formal demonstrations based on the declaimed text of Galen or Avicenna or Mondino were practically the sole opportunities afforded to either teacher or pupil for the investigation of the minuter details of the human frame. But in making this statement concerning the arrest of anatomical progress, we must expressly exclude the products of the mighty genius of Leonardo da Vinci (1452-1519), whose anatomical researches were without influence, and remained long unnoticed.[135] We must also omit evidence gathered from the work of such early Renaissance painters as Antonio Pollaiuolo (1429-98) or Andrea del Verrocchio (1435-88), for these pursued the study of anatomy in a special field and with a special object.[136] Furthermore, there are a number of artists of similar date of whose anatomical studies we have no direct evidence, but who yet outlined the muscles of the nude human figure in such a way as leads us to suppose that they had investigated the superficial structures at least of flayed parts. Such is the suggestion of some of the work of Luca Signorelli (_c._ 1442–_c._ 1524), and of Andrea Mantegna (died 1506). With such reservations, however, it is probably true that no evidence is forthcoming until the last decade of the fifteenth century of any advance from the standpoint of Mondino.[137] But if descriptive anatomy developed slowly in the hands of the physicians, the art of graphic representation of anatomical structures was still more backward. Several groups of anatomical drawings of mediaeval date have come down to our time, but examination of them shows that they have been drawn without direct reference to the human frame. Some of these figures are of the crude type known as the ‘five-figure series’ (Plate XXXIII), mere traditional diagrammatic sketches.[138] Hardly better or more instructive are the series of dissections which illustrate certain MS. works of Henri de Mondeville (Plate XXVIII _a_)[139] and Guido de Vigevano (Plates XXXI and XXXII), 1345.[140] A few sketches representing the separate organs have also survived (Fig. 6),[141] but these never suggest that the draughtsman had before him the structure which he seeks to depict, and the drawings appear to have been made in order to illustrate contemporary physiological theory rather than observed anatomical fact. Even the magnificent illuminated Dresden Codex of Galen, prepared in France or Flanders as late as the second half of the fifteenth century, betrays not the slightest first-hand knowledge of anatomy.[142] Although the illustrations of this MS. are prepared with the utmost technical skill, they yet show us a teacher exhibiting to his pupils a heart of the form found on playing-cards, and other anatomical figures scarcely more faithful to the facts (Plate XXXIV). [Illustration: Fig. 6. DIAGRAMS OF THE INTERNAL ORGANS After Bodleian Library MS. Ashmole 399 of about 1298, fos. 23 recto–24 recto.]