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.
In reading any early description of the eye, it is to be remembered
that until the nineteenth century the ‘emanation theory’ prevailed.
Light was regarded as of the nature of a stream of particles emitted
from the object seen, and the act of vision was considered as a
collision of this emanation with an emission of something from the eye
itself, called in mediaeval writings the ‘visual spirit’.
(_c_) THE HEART