438 
Proceedings of the Royal Soeiety 
occurs to 1°, so that while accommodated for infinity^ the eyes 
direct their visual axes to a point nearly 12 feet distant. Suppose, 
now, the eyes are accommodated for an object at the distance of 
12 feet. Surely now the accommodation and convergence will 
coincide ! No ; the right eye rolls inwards another 40'. The 
optic angle is therefore 1° 40'. It is easy to calculate trigonome- 
trically, knowing ray own intercentral distance, that the visual axes 
must now intersect rather more than 7 feet from the eyes, while 
accommodation takes place for nearly 12 feet (11 feet 8). 
The slightest increase of accommodation is associated with a 
sympathetic advance of convergence, and there is a decreasing 
interval between the two. The excess of convergence over accom- 
modation diminishes as the object of view approaches till a certain 
point, when they both coincide. This point in my own case* is 
56 inches distant. As the visual object approaches still nearer, 
convergence fails to keep pace with accommodation. With each 
increment of accommodation throughout there is a corresponding 
increment of convergence, but a smaller one. It is like a long- 
legged and a short-legged competitor in a race, in which both are 
bound to keep step, the shortdegged having a start, but the long- 
legged winning in the end. Being somewhat hypermetropic, my 
convergence would be expected to exceed my accommodation when 
the latter is negative, but strangely I have found the excess greater 
in most normal eyes I have tried than in my case, and to vary 
from 4° to I have not been able to experiment on many, but 
I have found it quite as much in one or two myopic patients. 
It raises the question, What is the position of rest of the eyes 
which they would assume in sleep ? 
I think it may be accepted as extremely probable that it is the 
natural condition of brain centres, at least those connected with the 
eye, to evolve some nerve energy, even in sleep. It is impossible 
for most people to relax their ciliary muscle completely without a 
distant object to look at, and even the faculty claimed by some 
oculists to be acquired by training, is received by their brethren 
with much incredulity. Evidently the degree of convergence, 
though it does not coincide with accommodation, is closely affected 
* I am unable to continue experiments on myself. 
