Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . ofdetermining whether anobject is hot or cold, dryor moist, hard or are some parts,however, the ends of thefingers, for example, inwhich this sensibility isespecially acute, and thesealso receive a larger supply of nerves. § 118. On the contrary, those parts which are destitute ofsensibility, such as the feathers of birds, the wool of animals,and the hair of man, are likewise destitute of nerves. But theconclusive proof that se
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . ofdetermining whether anobject is hot or cold, dryor moist, hard or are some parts,however, the ends of thefingers, for example, inwhich this sensibility isespecially acute, and thesealso receive a larger supply of nerves. § 118. On the contrary, those parts which are destitute ofsensibility, such as the feathers of birds, the wool of animals,and the hair of man, are likewise destitute of nerves. But theconclusive proof that sensibility resides in the nerves is, thatwhen the nerve which supplies any member of the body issevered, that member at once becomes insensible. § 119. There are animals in which the faculty of percep-tion is limited to this general sensation ; but their number issmall, and, in general, they occupy the lowest place in theseries. Most animals, in addition to the general sensibility,are endowed with peculiar organs for certain kinds of percep-tions, which are called the SENSES. These are five in number,namely : sight, hearing, smell, taste, and touch-. Fig. 36.—The Anatomy of Asteriasaurantiaca. 58 SPECIAL SENSES. SECTION II. OF THE SPECIAL SENSES. 1. Of Sight. § 120. SIGHT is the sense by which light is perceived, andby means of which, the outlines, dimensions, relative position,colour, and brilliancy of objects are discerned. Some of theseproperties may be also ascertained, though in a less perfectmanner, by the sense of touili. We may obtain an idea ofthe size and shape of an obji-rf, by handling it; but the pro-perties that have a relation t-> light, such as colour and bril-liancy, and also the form and size of bodies that are beyondour reach, can be recognized by sight only. §121. The EYE is the organ of vision. The number, struc-ture, and position of the eyes in the body is considerablyvaried in the different classes. But whatever may be theirposition, these organs,
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