302 1'IIYSIoU.XiY "! MUSCLES AM> NKKYKS. 



probable that in OIK- nerve-fibre .1 resistance (o transmiwion 

 exists, and in another an avalanche-like increase. All the 

 facts arc more easily and simply explained liy assuming that 

 there is a resistance to transmission in all nervi s, allowance 

 beiiiLjat tlie same time made tor the difference in the ex- 

 citability of dili' rent points in the nerve. 



.Moreover the curve of excitability in the case <,f the 

 sei.-Uic nerve is not a simple ascending line from the muscle 

 to the dorsal marrow. Thi> nerve is found, as is shown in 

 fig. 1'2, liy the union of several roots J it then, at variou.s 



Fn.. 7 1'. Tin: -< IATII- M:I:VI. AM> < AI.K-MIX 1.1: or A 



points, i\-es oil' ln-anches which enter the muscles of tie 

 upper h% and then separate into two branches, one of which 

 provides for the calf-muscle (f///.s7/-cV' IHIHH), the other for the 

 (lexor muscle of the lower ]e^. If various points of this 

 iicrxe are irritated ill the living animal, the net ve havin;,' 

 been merely exposed and isolated from the surrounding parts, 

 but not s-parated from the dorsal marrow, it i^ ver\ e\ iilcnt. 

 th;it the excitability at the upper points is generally Create!' 

 than at the lower; but p'int>are also found in the com se 

 of the nerve at which a greater excitaliility exists than at the 

 p lints above and below, as also, on the c. nti-ary. a lev-; i \ 

 citaliility than at the adjacent jioints. Such irregularities 

 are m.i-t abiindiintly exhibited at th- points \\here nerve- 

 brancln - separate from t he main trunk, especially when tl> 

 branches bave been cut a\\ay. This is partly due to clec- 

 t rot 01 iic iiillu -nci's (./'. p. 1 L'"> <l 8tq. \ |>. - 1 "> ' / >-'/ ^" tr ' : ^)- 

 The nerve libres which ai'e cut generate a i-urreiit which 



