70 Lr Graves on the Sense of Touch. 



iiishes abundant proofs, if any were wanting, of the wisest adap 

 tation of parts to the functions they are called on to discbarge. 

 Here is no unnecessary expenditure of tactile acumen, but a most 

 rigid economy of the sense of touch, which is nowhere spread 

 over surfaces indiscriminately, and without reference to their 

 other physical qualifications. This great difference was never 

 before suspected to exist ; it was indeed known that the tops of 

 the fingers, the tip of the tongue, and some other parts, enjoy 

 the sense of touch in a pre-eminent degree, and are capable of 

 judging much more delicately, concerning what they are placed 

 in contact with, than other portions of the body. This was at- 

 tributed partly to habit, partly to their shape, and many laid 

 great stress on the facility with which these extremely moveable 

 parts could be adapted and applied to bodies undergoing ex- 

 amination. Now, for the first time, has it been proved by We- 

 ber, that, quite independently of all these extraneous circum- 

 stances, the skin itself varies in the intensity of its tactile power ; 

 and that this arises not from the mere varying thickness of the 

 epidermis, and general delicacy of conformation in the cuta- 

 neous tissue, but from an original difference in its organization. 

 All these facts tend strongly to overturn the common hypothesis, 

 that the sense of touch is diffused throughout the whole texture 

 of the skin, and lender it much more probable that it is per- 

 formed only hf certain small organs, extremely minute, and in 

 size comparable to points, but differing much in their mode of 

 distribution, being very crowded together and numerous in some 

 parts of the ?kin, while in others they are more sparingly pre- 

 sent, and are, as it were, thinly scattered. On this supposition 

 alone, we can account for the signal differences in tactile dis- 

 cernment, which the different portions of the skin exhibit. The 

 researches of Breschet, to which the attention of the English 

 public was first drawn, by an able analysis by my friend Dr 

 Gostello, published in the Dublin Medical Journal for Septem- 

 ber 1835 ; these researches have rendered it certain, that the 

 sense of touch is performed by a less simple apparatus than was 

 generally imagined. M. Breschet considers that the nerve parts 

 with its neurilema at the derma, as the optic nerve does in en- 

 tering the sclerotic, and that the projecting papillae take a new 

 envelope from the outer surface of the derma ; that the mere 



