( 356 ) 



the grejilor toiisioii c.-uiso llic lalci-al part lo l)0('(nne iii8ensil)le 

 earlier than the ventral paii. 



This o|>iiii(»ii is supitoi-tcd liv llir tads w hicli we iiiav ohscrxe, when 

 com pressing' a jxM-iplierieal nerve, c u. llic nerxiis nhiaris. In that 

 case too, llie sensil)ilily for |»ain-slininH >lo\\ Iv dies awav IVoni tlic 

 |)eri])liery of tiie innei-\ation-area on the skjji to\\ar(ls iis centrum, 

 i.e. the ('iitraiicc |ihic<' of tins ncr\"c into the inncrxation-area. 



The I'ecent connniinications of SnKinnNCiTON ^) loo. ap|>arenlly |»oint 

 to this same fact : the cciiiral areas dvinci' a\\ay slowly in a 

 centi'ipetal direction. 



His lliird concliisioii especially may he said to lie of importance 

 in this mattei': "•In the --kin of macacn> tlir •■pain-lidd' and the 

 "heat-lield" of a sinuic sensory spinal root, at least in the case of 

 certain spinal nerxes, are each less {'.xteiisix-e than is the ■■tonch-lield" 

 of the same root." 



As in onr experiments the slinndi employe<l weix' exclnsixely 

 maximinn paiii-stimidi, a donl)t may arise, whether onr cenli-al-areas 

 onghl not to he considei'e(l simply as those areas of the dei'inatoma 

 that are sensihk' to pain. The |(ecnliar way. in which the intensity 

 of the operatixc ti-anma exerts its iidlnence on the form of tiie 

 central area, rendei-s tlii> siip|)osition hiuhly improliahle. .Mnch more 

 [)rohal)le it is, that llie hefore-ment.'oiied conclnsion of Siiki{KIN(.ton 

 expresses in a different inannei- thai the paiii-seiisiltility in sensihje 

 skin-areas is dyijiu- away in a centripetal direction, 'llie sensihility 

 for pain how exei- and the nlnaris-experimenl also points this 



wav — is htst mnch sooner than the sense of loncii. Experinieiils 

 ma(k^ hy one of ns on sharks, thai will he comnnmicate(l afterwards. 

 are in accoi'dance with this observation. 



Both the pecnliar proportions of the |)(M'ipherical skin-ijiner\ation 

 (entrance-[)laces. extension-areas of the skin-hranclies in tlie root-area), 

 and the «ieneral rnles for the nerve-condnction, are therefoi'e of 

 eqnal importance for determiniiiL'- experimentally the form of the 

 dermatonjata. 



Becanse three afferent nerves of difterejit siunilicance iimerve three 

 pieces of the trnnkdermatoma. possessinji' each of them a ditferent 

 degree of extension, the sensihility for pain, decreasing (in cases of 

 j)rGgressive lesions) in a centripetal direction, xvill be the canse of the 

 appareiitly capi-icionsly-sha[)e(l central areas, described in the conrse 

 of onr obser\ations. 



1) Sherrington, On dissociative anaoslliosia (Jininial of Pliysiology. vol. :27, 

 1901 -'02). 



