▁the ▁skin ▁and ▁some ▁parts ▁of ▁the ▁m uc osa ▁of ▁all ▁verte br ates . ▁In ▁m amm al ian ▁skin , ▁they ▁are ▁clear ▁cells ▁found ▁in ▁the ▁str atum ▁bas ale ▁( at ▁the ▁bottom ▁of ▁swe at ▁du ct ▁rid ges ) ▁of ▁the ▁e pid erm is ▁approximately ▁ 1 0   μ m ▁in ▁diameter . ▁They ▁also ▁occur ▁in ▁e pid erm al ▁inv agin ations ▁of ▁the ▁plant ar ▁foot ▁surface ▁called ▁re te ▁rid ges . ▁Most ▁often , ▁they ▁are ▁associated ▁with ▁sens ory ▁n erve ▁end ings , ▁when ▁they ▁are ▁known ▁as ▁Mer kel ▁n erve ▁end ings ▁( also ▁called ▁a ▁Mer kel ▁cell - neur ite ▁complex ). ▁They ▁are ▁associated ▁with ▁slowly ▁adapt ing ▁( SA 1 ) ▁som atos ens ory ▁n erve ▁fib ers . ▁They ▁react ▁to ▁low ▁v ibr ations ▁( 5 – 1 5 ▁H z ) ▁and ▁deep ▁static ▁touch ▁such ▁as ▁shapes ▁and ▁edges . ▁Due ▁to ▁a ▁small ▁re cept ive ▁field ▁( ext rem ely ▁detailed ▁info ) ▁they ▁are ▁used ▁in ▁areas ▁like ▁f ing ert ips ▁the ▁most ; ▁they ▁are ▁not ▁covered ▁( sh elled ) ▁and ▁thus ▁respond ▁to ▁press ures ▁over ▁long ▁periods . ▁ ▁Development al ▁The ▁origin ▁of ▁Mer kel ▁cells ▁has ▁been ▁deb ated ▁for ▁over ▁ 2 0 ▁years . ▁Ev idence ▁from ▁skin ▁gra ft ▁experiments ▁in ▁birds ▁implies ▁that ▁they ▁are ▁neural ▁cr est ▁derived , ▁but ▁experiments