CHAPTER I 



THE PHYSIOLOGY OF THE SENSE OF TOUCH 



The bearing of the foregoing facts and observations, macro- 

 scopical and microscopical, on the Sense of Touch in Mammals 

 and Birds must now be considered, but, before entering the 

 region of interpretation, it is desirable to allude briefly to the 

 history of the subject. 



The sense of touch in animals below man has apparently 

 been little investigated, though certain interesting studies of 

 this sense have been made in isolated groups of the subject, 

 notably those of Spallauzani on the tactile sense of bats, already 

 referred to, and on the special minute anatomy of the nerve- 

 endings of the snouts of moles, by Eimer, and in the snouts of 

 pigs, where also peculiar branched axis-cylinders terminate in 

 concavo-convex enlargements between the deeper epitheUal 

 cells (Quain). But beyond such occasional investigations of 

 the sense of touch, and the well-known studies of Weber on that 

 of man, there is httle to record. The history of the subject 

 resolves itself into the very extensive researches, which have 

 been made by numerous investigators, into the papillary ridges 

 of the hand of man, and of later years, into those of the hand 

 and foot of lower animals. The amount of hterature connected 

 with these ridges is immense, and all that I have been able to 

 collect from various sources is given in full in an Appendix. A 

 long paper written in 1905 by Schlaginhaufen, gives an exhaustive 

 hst of the communications on the subject and this occupies four 

 and a half pages. Altogether, not fewer than one hundred and 

 twenty memoirs and books, bearing on this subject, have been 

 collected by the industry of Schlaginhaufen and others. 



The papillary ridges on the hand of man first attracted serious 



