ZOOLOGICAL SOCIETY BULLETIN 



PUFFER 



Interior Oblique, one of the two muscles of accom- 

 modation. 



Inferior Rectus, the muscle which turns the eyeball 

 downwards. 



Superior Rectus, the 



two muscles of accom- 

 vhieh turns the eyeball 



out producing any cliange in tiu' focus of the 

 eyes of the fish. 



6. Electrical stimulation now changed the 

 focus from distant to near objects, as it did in 

 the beginning. 



It was interesting to observe that in those 

 fish which did not have two oblique muscles, 

 electrical stimulation failed to change the fo- 

 cus of their eyes from the distance to a near 

 point. In one, the dog fish, with one oblique 

 muscle, accommodation or near focus was not 

 produced by electrical stimulation ; but, after 

 the place of the absent muscle was supplied by 

 a thread of silk, then the focus of dog fish's 

 eyes was changed to a near point wlien they 

 were stimulated with electricity. After the 

 oblique muscles were removed from the eye of 

 a fish and when the eye had healed, some weeks 

 later, near focus or accommodation could not 

 be produced by electrical stimulation. 



DIAGRAM OF HUMAN EYE 



One inch long from a person. 00 inches tall. Note the nearly 



spherical .shape. The optic nerve entrance is at 



the inner side. 



In another series of experiments, tiie lens of 

 a fish's eye was removed. A pearl roach six 

 inches long was examined. The eyes were not 

 near-sighted. Electrical stimulation produced 

 considerable change and the eyes were focussed 

 for a near point. The lens of tlie eye was 

 pushed to one side of the axis of vision, when 

 the eye became very far-sighted. Electrical 

 stimulation of the eye now produced marked 

 accommodation. This experiment confirmed 

 others that the lens was not necessary to change 

 the focus from distant objects to those which 

 were near. While I was otherwise engaged, 

 IJr, C. Barnert performed the same experiment 

 successfully on the eye of a carp. He pushed 

 the lens to one side, applied the electric cur- 

 rent, and produced near-sight or accommoda- 

 tion in a few minutes, all without assistance. 

 Electrical stimulation produced as much accom- 

 modation after the removal of the lens as be- 

 fore. The fact that accommodation in the eyes 

 of fish is not produced by the action of the lens 

 inside of the eyes, but is accomplished by the 

 two oblique muscles outside of the eyes, is one 

 of great practical value. The investigations 

 further showed that fish could be made near- 

 sighted, far-sighted or astigmatic by various 

 operations upon the oblique muscles. 



Of what value was the study of fishes' eyes 

 to people with poor sight wearing glasses? In 

 brief, the cause of the need of glasses was 

 learned and it suggested treatment successful 

 in relieving near-sight, far-sight, astigmatism 

 and presbyopia or old age sight without glasses. 



