2 ACCOUNT OF THE FOKAMEN CENTRALE 
peculiar to man, or was extended to other species of ver- 
tebral animals. The result of these inquiries, so far as I 
have been able to collect, is as follows. 
— " In Man," (observes Bar#n Cuvier, Anaf. Compar. 
t. ii. p. 422.), " there is, near the entry of the nerve, and 
almost at the point which corresponds to the axis of the 
eye, a small fold of the retina, which forms a slight con- 
vexity, when the more external membranes are removed. 
In the midst of this fold there is a transparent point, which 
at first sight appears like a hole ; the edges of this point 
are tinged with yellow in adults, but not in the new-born 
infant. This peculiarity of the human eye, which had 
escaped the observation of all anatomists before S(emme- 
RiNG, is found in no other animal, except in monkeys. We 
have observed it in the Cynoceplialus, in the White-nosed 
Guenon, &c. In the first, the transparent part is consider- 
ably larger than in man, and of an oval form : there is 
sometimes a yellow spot at its side. 
" The Maki, which of all Mammalia approaches nearest 
the monkeys, has only a slight fold, without any spot or 
transparent point. The other species have nothing simi- 
lar.'' 
These facts, and others, relative to the pathology of this 
foramen in the human retina, were pointed out by many 
distinguished comparative anatomists. The yellow spot or 
tinge, more or less surrounding the foramen, is said to be 
wanting when vision has been obstructed ; and the plait is 
small and wrinkled. In monkeys, the yellow spot is occa- 
sionally absent. The important fact, that the appearances 
are limited to the eyes of man and a few quadrumanous 
animals, has been much dwelt on by physiologists, whilst 
the existence of a foramen^ or transparent point of the 
membrane of the retina, situated in the actual line of vi- 
sion, has been deemed by most absolutely inexpHcable. 
