CONTENTS. 



SECTION V. 

 Comparative Physiology and Morphology of Nervous System. 



Introductory. — Outline of the classification of animals, 70. 

 Comparative Morphology of the Vertebrate Nervous System. — Gen- 

 eral plan of structure, 72. 



Brain of Vertebrates. 



(1) Variation in size, absolute, 72 ; and relative, 73. (2) Relative 

 amount of gray matter, 74. (3) Relative size of cerebrum, 76. Owen's 

 classification of mammals, 77. Pineal gland, 78. Embryonic and 

 taxonomic series compared, 79. (4) Relative size of frontal lobe, 

 82. Cephalization, 82. 



SECTION VI. 



Nervous System of Invertebrates. 



1. Articulata. — General plan of structure compared with vertebrates, 

 84. General plan of nervous system, 85. Functions of the several 

 ganglia, 86. Modifications in going down and up the scale, 87. 



2. Mollusca, 89. — General plan of nervous system, 90. 



3. Radiata. — General plan of, 92. 



4. Protozoa have no nervous system, 93. 



CHAPTER II. 



SENSE ORGANS. 



SECTION I. 



Introductory. 



Relation of special sense to general sensibility, 94. Illustration of 

 the law of differentiation, 95. Gradations between the senses : (1) 

 In perception of vibrations, 96 ; (2I in kind of contact, (3) in objec- 

 tiveness, 97. Higher and lower senses, 98. 



Sense of Sight and its Organ, the Eye. 

 Primary divisions of the subject, 98. 



SECTION II. 

 Eye of Man — General Structure. 



Shape, setting, 99. Muscles, 100. Coats of the ball, 101. Lin- 

 ings, contents or lenses, 102. 



Formation of the Image, 103. — Necessity of lenses, 104. Applica- 

 tion to the eye, 105. Proof of retinal images, 106. 



Comparison of the Eye and the Camera. — Defects of lenses and 

 their correction : (1) Chromatism, 107 ; (2) aberration, 108. Accom- 

 modation, Helmholtz's theory of, 109. Adjustment for light, in. 

 Structure of iris, 112. 



Defects of the Eye as an Optical Instrument. — Normal sight — em- 

 metropy, myopy, 113. Hyperopy, presbyopy, 114. Astigmatism, 115. 



