INTRODUCTION 



The sense of touch in the lower animals might be held to include 

 extremely wide range, and could not be fairly limited to 

 mammals and birds if it were not that the most important part 

 of the subject centres round this sense as found in the hand and 

 foot. Its present consideration has, therefore, special reference 

 to the papillary ridges and papillae of the corium ; and this alone 

 afEords a wide enough area of investigation, considering the very 

 large number of mammals in which these structures are present. 

 Such varied developments of the sense of touch, as are seen in 

 the surface of the tongue, in tactile hairs, especially the vibrissse 

 on the muzzles of felidee, the antennae and tactile hairs of insects, 

 the highly sensitive vascular snouts of moles, the dehcate vibrissas 

 of the snouts and the tactile organs of the wing- membranes 

 and ear-conchs of bats, in whom the sense of touch seems to be 

 developed almost to perfection — these, to take a few of the 

 striking adaptations among animals for the sense of touch, are 

 examples of a different kind and are not included in this study. 



It is clear that the sense of touch is a very important element 

 in the complex hfe of man, and, from the time of Weber, it has 

 been studied on experimental lines with valuable results. These 

 will be referred to in their own place under the physiological 

 section of the subject. But it is necessary to state that the 

 method of treatment of the sense of touch here pursued is ex- 

 clusively anatomical. Certain experiments have been made by 

 biologists on this sense in the lower animals, notably those of 

 Spallanzani in 1793, on the dehcacy of the tactile sense of bats, in 

 whom the sense of sight was artificially destroyed, and these 

 jnelded most interesting results. But the investigation of a 

 sense so much dependent on direct communication between the 



