71G 



to A. Fischer^) is only '/H of that in those slow oesophagus nerves 

 of the Hoj'se. Göthlin adds to this (p. i6) that onlj by assuming 

 the intluxion to be conducted in the same way in the nerve fiber 

 as electricity in a cable, it is to be understood why the velocity of 

 conduction varies according to the dimensions of the fibers. With 

 the thickening of the medullary sheath, which serves as "relative 

 isolator", the capacity of the cable evidently diminishes, and with 

 the enlargement of the area of section of the "conducting" axis 

 cylinder, the resistance of the cable diminishes. In fact then they 

 equally enhance the conductivity of (he nerve fiber, and thus it 

 becomes comprehensible that (as Donaldson and Hoke and also others 

 found) the mean area of section of the medullary sheath in all 

 vertebrates remains equal to that of the axis cylinder, which it 

 envelops. However, Göthlin again justly points this out, the nerve 

 fiber should by no means be imagined as an ecpially passive con- 

 ductor as e.g. a telegraph wire. On the contrary, njany circumstanceg 

 render it necessary to assume that in all long nerv« fibers which 

 are rapid conductors, the influxion is regenerated in some way or 

 other during its conduction, and thus compensates for the losses of 

 energy during the propagation in an ever enlarged space*). 



Chauveau evidently supposed' a relation between the greater or 

 smaller rate of conduction of the "excitations" in the nerves, and 

 the voluntary or involuntary character of the movements they excite. 

 It is pretty firmly established now that we have to think here of 

 inore tangible causes. 



Qui' knowledge took an important step forward by Carlson's 

 researches (in 1904 and 1906)'). He demonstrated that for Reptiles 

 (Snakes), Amphibians (Frog), Fishes (the Califoniian Hagfish Bdello- 

 stoma), T'ephalopods (Octopus, Loligo), Gastropods (Slug Limax, 

 Ariolimax, Sea hare Pleurobranchaea) and Crustaceans (Spider Crab, 

 Lobster, Limulus) there exists proportionality between the rale of 

 propagation of the impulses in the motor nerve and the coi»traction 



1) A. Fischer, Ein Beitrag zur Kenntnis des Ablaufs der Erregungsvorgauge im 

 marklosen Warmbliiternerven. Giessen 1911. of. Göthlin, p. 15. 



5) Gf: J. B. Johnston, On the Significance of the Galiber of the Parts of the 

 Neurone in Vertebrates. Journal of Comparative Neurology and Psychology. Vol. 

 18. Philadelphia 1908, p. 609—618. 



^) A. J. Carlson, The Rate of the Nervous Impulse in the Spinal Cord and in 

 the Vagus and the Hypoglossal Nerves of the Galifornian Hagfish (Bdellostoma 

 Dombeyi). American Journal of Physiology. Vol. X. Boston 1904, p. 401—418. 



, Further evidence of the direct relation between the Rate of Conduction in 



a Motor Nerve and the Rapidity of Contraction in the Muscle. Ibid. Vol. XV. 

 Boston 1906, p. 136—143. 



