ABSTRACT
In the table of the dimensions of some parts of the eye, which, for convenience of reference, is given together below, it will be seen that the diameter of the blind spot is considerable compared with the size of the retina, its greatest diameter being about 8/100 in. The following are the dimensions in English inches of some parts of the eye: By means of an instrument to be presently described, the ophthalmoscope, it is possible to view directly the whole surface of the retina, and to observe the inverted images of the objects there depicted. Until within the last few years it has been most confidently asserted by many authors that the eye, considered as an optical instrument, is absolutely perfect, and entirely free from certain defects to which artificial instruments are liable. There is a property of the eye which has led to the production of many amusing and curious illusions.
