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CHAPTER II. 



TOUCH. 



I HAVE already had occasion to point out the structure of 

 the integuments, considered in their mechanical office of 

 protecting the general frame of the body;* but we are not 

 to view them in their relation to the sense of touch, of which 

 they are the immediate organ. It will be recollected that 

 the corium forms the principal portion of the skin; that the 

 cuticle composes the outermost layer; and that between these 

 there occurs a thin layer of a substance, termed there/e mu- 

 cosum. The corium is constructed of an intertexture of 

 dense and tough fibres, through which a multitude of blood 

 vessels and nerves are interspersed; but its external sur- 

 /ace is more vascular than any other part, exhibiting a fine 

 and delicate net-work of vessels, and it is this portion of 

 the skin, termed by anatomists the vascular plexus, which 

 is the most acutely sensible in every point: hence we may 

 infer that it contains the terminations of all the nervous fila- 

 ments distributed to this organ, and which are here found to 

 divide to an extreme degree of minuteness. 



When examined with the microscope, this external sur- 

 face presents a great number of minute projecting filaments. 

 Malpighi first discovered this structure in the foot of a pig; 

 and gave these prominences the name of papilla. It is pro- 

 bable that each of these papillae contains a separate branch 

 of the nerves of touch, the ultimate ramifications of which 

 are spread over the surface: so that we may consider these 

 papillae, of which the assemblage has been termed the cor- 

 pus papillare, as the principal and immediate organ of 



* Vol. I. p. 90. 



