The External Muscles of the Eyeball 39
might have inquired more carefully into these cases, and if he had, he might have been less dogmatic in his state ments ; for, as has been pointed out in the preceding chap ter, there are plenty of indications that the contrary is the case. In my own experiments upon the extrinsic eye muscles of fish, rabbits, cats, dogs and other animals, the demonstration seemed to be complete that in the eyes of these animals accommodation depends wholly upon the action of the extrinsic muscles and not at all upon the agency of the lens. By the manipulation of these muscles I was able to produce or prevent accommodation at will, to produce myopia, hypermetropia and astigmatism, or to prevent these conditions. Full details of these experi ments will be found in the "Bulletin of the New York Zoological Society" for November, 1914, and in the "New York Medical Journal" for May 8, 1915; and May 18, 1918; but for the benefit of those who have not the time or inclination to read these papers, their contents are summarized below.
There are six muscles on the outside of the eyeball, four known as the "recti" and two as the "obliques." The obliques form an almost complete belt around the middle of the eyeball, and are known, according to their position, as "superior" and "inferior." The recti are attached to the sclerotic, or outer coat of the eyeball, near the front, and pass directly over the top, bottom and sides of the globe to the back of the orbit, where they are attached to the bone round the edges of the hole through which the optic nerve passes. According to their position, they are known as the "superior," "inferior," "internal" and "ex ternal" recti. The obliques are the muscles of accommo dation ; the recti are concerned in the production of hyper metropia and astigmatism.