. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. 114 PHYSIOLOGY. upon the tactile surface, we discover the roughness or smooth- ness of the substance. The knowledge of form and iveight is derived by the additional assistance of the muscular sense. The sense of touch is exceedingly educable, as is seen in the case of the blind, who can be taught to read, and even distinguish colours by its agency. Impressions made upon the organ of touch continue perceptible for som
. An analytical compendium of the various branches of medical science, for the use and examination of students. Anatomy; Physiology; Surgery; Obstetrics; Medicine; Materia Medica. 114 PHYSIOLOGY. upon the tactile surface, we discover the roughness or smooth- ness of the substance. The knowledge of form and iveight is derived by the additional assistance of the muscular sense. The sense of touch is exceedingly educable, as is seen in the case of the blind, who can be taught to read, and even distinguish colours by its agency. Impressions made upon the organ of touch continue perceptible for some time after the stimulus has been removed; for instance, the stinging of a smart blow does not soon subside, and ihe simple con- tact of an article of clothing often leaves the impression of its presence after it has been removed. The subjective sensations pertaining to the nerves of this sense are among the best known. The tingling of a limb that is " asleep^'' which commonly depends on pressure on its trunk, may also result Fig. 31.* from changes in the centre; the same is true of formica- tion, heat, chilliness, itching, and also of pain. SENSE OF TASTE. In the sense of taste, as well as in touch, the substance to be examined must be brought into contact with the organ of the sense, which organ is the mucous membrane of the tongue and fauces. The mu- cous membrane of the tongue is largely supplied with papillae of various forms, which are abundantly supplied with nerves and blood-vessels. The papillse are of three varieties ; 1st. The calycifortn, or cir- cumvaUate^ situated at the base of the tongue in a V shaped line, a (Fig. 31); the fungiform, on the sides and apex, b ; and the conical, or filiform, the most numerous, and most abundant, in the cen- tral part, d. The latter are supposed to be concerned rather in the sense of touch than of taste. When these papillse are called into * Upper surface of tongue, a. One of the circumvallate papillae ; b. one of the fungif
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