1912.] The Process of Excitation in Nerve and Muscle. 511 



contraction and to the liberation of heat we have to deal with processes 

 which are apparently absent from nerve and are therefore on the first 

 showing not essential to propagation. We must not dismiss the matter quite 

 so lightly. The possibility that these phenomena really constitute a part of 

 the propagation process, reduced in nerve to minimal dimensions, is not to be 

 overlooked. 



Bose,* arguing from the general probability that in all the excitable tissues 

 the fundamental phenomena are identical, each particular aspect being 

 merely accentuated in accordance with functional requirement, was led to try 

 whether nerve was able to contract. By an optical method he found that 

 electric currents from an induction coil did cause the nerve to shorten. 

 That this shortening was the analogue of muscular contraction was not 

 proved, and Wallerf was led by his own experiments to regard it merely as 

 a result of the heating effect of the "stimulating " current. 



Quite apart from such evidence, there is a large body of experiment 

 showing that the propagated disturbance may continue in a muscle which 

 has been rendered unable to contract. BiedermannJ was the first to bring 

 evidence of this nature. He reported that a muscle steeped for part of its 

 length in distilled water was no longer able to contract in that part, but was 

 still able to transmit a propagated disturbance. The validity of these 

 experiments was energetically denied by Kaiser,§ but seems to have been 

 established by the later work of Overton|| and Hartl.1T The experiments of 

 Hartl are particularly valuable, because they were so devised as to exclude 

 by special precautions the possibility that the apparent passage of a 

 propagated disturbance through the non-contractile part of the muscle 

 rested in reality on a spread of the exciting current to the part which 

 remained normal. Hartl found disproof of such a possibility in the long 

 delay which his experiments showed between the passage of the exciting 

 current in the altered part of the muscle and the appearance of contraction 

 in the normal part. The disturbance was evidently propagated slowly 

 through the water-logged muscle. The danger which besets the interpretation 

 of experiments of this type is, of course, that there may have been in the 

 water-logged part of the muscle a central core of fibres not yet completely 

 robbed of their ability to contract, yet too feeble to bring about a visible 

 shortening of the whole muscle. Such fibres might have served to propagate 



* Bose, 1 Comparative Electrophysiology,' 1907, p. 507. 



t Waller, ' Proc. Physiol. Soc.,' March, 1908 ; ' Journ. Physiol.,' vol. 37. 



\ Biedermann, 'Stzber. d. k. k. Akad. Wien.,' 1888, vol. 97, III, p. 101. 



§ Kaiser, ' Zeitschr. f. Biol.,' 1895, vol. 31, p. 244. 



|| Overton, 'Arch. f. d. ges. Physiol.,' 1902, vol. 92, p. 146. 



IT Hartl, ' Arch. f. ( Anat. u.) Physiol.,' 1904, p. 80. 



