PHYSIOLOGY. 



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cochlea (p ) ; and the auditory nerve (o). This subject embraces 

 the theory of sound, including the nature of sound and its mode 

 of transmission, and the mechanism of hearing or the transmis- 

 sion of sound through the different portions of the ear. 



The Sense of Sight. 

 Under this head are comprised the apparatus for its protec- 

 tion (PL 3, fig. 5), embracing the brows, the orbit, the eyes, 

 the eyelashes, the lachrymal gland (k), the lachrymal points, the 

 lachrymal ducts, and the nasal duct — the apparatus of motion, 

 consisting of eight muscles, viz., those which move the lids (the 

 orbicular e and levator of the upper lid), and those which move 

 the ball, the great oblique (1), the small oblique (g), the four 

 straight muscles (f, i and d) — the globe of the eye (fig. 6), 

 including the conjunctiva (b), the sclerotic membrane (s), the 

 choroid membrane (ch), the retina (r), the iris (i), the pupil 

 (p), the cornea (c and fig. 5, a), the aqueous humour, the crys- 

 talline humour (ca), the vitreous humour (o), and the optic 

 nerve (n and fig. 5, c) — and finally it includes the subject of 

 light, embracing its nature, direction, reflection, refraction (fig. 

 7, 8 and 9) and decomposition, together with the mechanism 

 of vision, or the progress of the luminous rays into the eye 

 (fig. 10). 



The Nervous System of Organic Life> 

 Or the great sympathetic, is composed of ganglions, united 

 among themselves by nervous cords, and forming a double 

 chain on both sides of the vertebral column, extending from 

 the head to the pelvis. 



This nervous system presides over the organs of involun- 

 tary motion, such as the heart, the stomach and the intestines. 



LOCOMOTION. 



Animals are not only capable of receiving impressions 

 from external objects ; they can likewise avoid or approach 

 these objects at will. This faculty is termed the faculty of 

 locomotion. It is effected by means of two apparatus, one 

 active (the muscular apparatus), the other passive (the bony 

 apparatus). There is another faculty besides that of sensa- 

 tion and of locomotion, which completes the life of relation ; 

 it is the power enjoyed by a great number of animals of 



