viii CONTENTS. 



SECTION III." 

 ON THE STRUCTURE OF THE INVESTMENTS OF THE RETINA. 



PAGE 



712. The Sclerotic Coat 21 



713. The Choroid Coat . 21 



714. The Ciliary Processes 23 



713. The Iris 24 



710. The Cornea 25 



717. The Ciliary Zone 20 



718. The Ciliary Muscle 28 



719. The Lens 28 



720. The Vitreous Humour and the Suspensory Ligament 29 



SECTION IV. 



THE MECHANISM OF ACCOMMODATION AND THE MOVEMENTS OF 

 THE PUPIL. 



721. The Mechanism for Changing the Anterior Curvature of the Lens 31 

 722. The Evidence that such a Mechanism does effect the Result . . 32 



The Movements of the Pupil. 



723. Circumstances leading to Constriction and to Dilation of the Pupil 34 



724. How Constriction and Dilation are brought about 34 



725. The Nerves supplying the Pupil . . 35 



726. Constriction a Reflex Act by means of the Optic and Oculo-motor 



Nerves 37 



727. Changes in the Pupil through the Action of the Cervical Sympa- 

 thetic Nerve 40 



728. The Nature of the Dilating Mechanism 41 



729. Direct Action of Drugs and other Agencies on the Pupil . . . 13 



730. The Nervous Mechanism of Accommodation 45 



731. The Association of the Movements of Accommodation and the 



Movements of the Pupil 40 



SECTION V. 

 IMPERFECTIONS IN THE DIOPTRIC APPARATUS. 



732. Imperfections of Accommodation 47 



733. Spherical Aberration 48 



734. Astigmatism 48 



735. Chromatic Aberration 50 



736. Entoptic Phenomena 51 



