44 Accommodation: Experiments on Animals
produced by electrical stimulation; but after the effects of the atropine had passed away, or a divided muscle had been sewed together, accommodation followed electrical stimulation just as usual. Again when one oblique muscle was absent, as was found to be the case in a dogfish, a shark and a few perch, or rudimentary, as in all cats ob served, a few fish and an occasional rabbit, accommoda tion could not be produced by electrical stimulation. But when the rudimentary muscle was strengthened by ad vancement, or the absent one was replaced by a suture which supplied the necessary countertraction, accommo dation could always be produced by electrical stimulation. After one or both of the oblique muscles had been cut, and while two or more of the recti were present and active,1 electrical stimulation of the eyeball, or of the nerves of accommodation, always produced hyperme-tropia, while by the manipulation of one of the recti, usually the inferior or the superior, so as to strengthen its pull, the same result could be produced. The paralyzing of the recti by atropine, or the cutting of one or more of them, prevented the production of hyperme tropic refraction by electrical stimulation; but after the effects of the atropine had passed away, or after a divided muscle had been sewed together, hypermetropia was pro duced as usual by electrical stimulation.
It should be emphasized that in order to paralyze either the recti muscles, or the obliques, it was found necessary to inject the atropine far back behind the eyeball with a hypodermic needle. This drug is supposed to paralyze the accommodation when dropped into the eyes of human
1 In many animals, notably in rabbits, the internal and external recti are either absent or rudimentary, so that, practically, in such cases, there are only two recti, just as there are only two obliques. In others, as in many fish, the internal rectus is negligible.