|
CHAPTER IV
THE TRUTH ABOUT ACCOMMODATION AS DEMON STRATED BY EXPERIMENTS ON THE EYE MUS CLES OF FISH, CATS, DOGS, RABBITS AND OTHER ANIMALS
T
HE function of the muscles on the outside of the eyeball, apart from that of turning the globe in its socket, has been a matter of much dis pute; but after the supposed demonstration by Helm-holtz that accommodation depends upon a change in the curvature of the lens, the possibility of their being concerned in the adjustment of the eye for vision at different distances, or in the production of errors of re fraction, was dismissed as no longer worthy of serious consideration. "Before physiologists were acquainted with the changes in the dioptic system,"1 says Donders, "they often attached importance to the external muscles in the production of accommodation. Now that we know that accommodation depends on a change of form in the lens this opinion seems scarcely to need refuta tion." He states positively that "many instances occur where the accommodation is wholly destroyed by paraly sis, without the external muscles being the least im peded in their action," and also that "some cases are on record of paralysis of all or nearly all of the muscles of the eye, and of deficiency of the same, without diminu tion of the power of accommodation."2
If Donders had not considered the question settled, he
1 The refractive system.
2 On the Anomalies of Accommodation and Refraction of the Eye, p. 22.
38 |
||