CONTENTS. xxxiii 



SECTION VIII. 

 The Lymphatic Arrangements of the Brain and Spinal Cord. 



PAGE 



§517. The characters of the cerebrospinal fluid 824 



§ 518. The renewal of the cerebro-spinal fluid. The purposes served by 



the fluid 825 



SECTION IX. 



The Vascular Arrangements of the Brain and Spinal Cord. 



§ 519. The distribution and characters of the arteries of the brain . . 827 



§ 520. The venous arrangements of the brain 828 



§ 521. The supply of blood to the brain relatively small. The methods of 



investigating the circulation of the brain 829 



§ 522. The supply of blood to the brain modified by the respiration and by 



changes in the general arterial pressure. The want of clear 



proof of special vasomotor nerves for the cerebral arteries . . 831 

 § 523. The flow of blood through the brain nevertheless influenced by 



changes taking place in the brain itself 833 



CHAPTER III. 

 Sight. 



SECTION I. 



On the General Structure of the Eye, and on the Formation of 



the Retinal Image. 



§ 524. Dioptic mechanisms and visual impulses 834 



§ 525. The general structure of the eye. The formation of the retinal 



image 835 



§ 520. A simple optic system ; its cardinal points. The refractive surfaces 



and media of the eye 839 



§ 527. The optic constants of the eye. The diagrammatic eye . . .841 



§ 528. The paths of the rays of light through the eye 843 



§ 529. The retinal image in relation to the sensations excited by it . . 845 



SECTION II. 



The Eacts of Accommodation. 



§ 530. The eye can accommodate for far and near objects ; far and near 



limits of accommodation 846 



§ 531. Scheiner's experiment 847 



