124 
ANNIVERSARY ADDRESS 
the Quakers as among the rest of the community has led Francis 
Galton to suggest that it may have been a physiological basis for 
the opinions of the founders of the sect “that the fine arts were 
worldly snares,” and also for their conspicuous practice of dressing 
in drabs. Nothing can be done for the colour-blind by either 
oculist or optician, for the anatomical basis of colour-sensation is 
unknown. The absence of cones in the retinas of nocturnal animals 
has led to the suggestion that these nerve-endings are concerned in 
colour-vision, but we do not know that these animals are colour¬ 
blind. The theory appears, indeed, to be confirmed by the absence 
of the other special nerve-terminals (the rods) of the retina in the 
yellow spot, which is full of close-set cones, and is most sensitive 
to colour rays, yet, as Foster observes : “ the fact may equally tend 
to prove that the rods are of no use in vision at all.” There are no 
rods in the retina of snakes. 
The interesting discovery that the colour of the outer limbs of the 
rods of the retina is due toapigment called “the visual purple,’’which 
is bleached by exposure to light and restored to its natural colour by 
darkness, appears to open the way to further knowledge of colour- 
sensation. Images can be fixed like a photograph on the visual 
purple, but the question of its function remains to be solved. This 
must also be said of the red and yellow globules of oil which 
are found in some of the cones of the retina of birds, reptiles, and 
amphibians. It has been suggested that these globules would shut 
off almost completely from their cones, blue light, which would only 
reach the cones without globules. The red globules would admit 
red light, and yellow and green light would enter through the 
yellow globules. The theory is attractive, but it is not proved. 
The Perception op Sight. 
The images of external objects are all inverted and reversed 
on our retina, or in other words topsy-turvy. The top becomes 
the bottom, and the right of the object becomes the left of the 
image. It is generally supposed that in our infancy our sense 
of touch enabled us to see things in their proper position, and so 
complete was the lesson and so constant has been the practice, that 
we now can with difficulty imagine we ever saw them otherwise. 
This is an unsatisfactory explanation, for there are many physio¬ 
logical facts which contradict it. For instance, when we view 
objects with our head between our legs, our position is that of a 
man standing on his head, and yet the objects we see are not 
inverted. Cases are recorded in which persons have obtained sight 
for the first time in after life through an operation, and they have 
