236 PHYSIOLOGY OF MUSCLES AND NERVES. 



quarter of au hour by allowing his imagination to 

 carry the hypotheses further than the point up to 

 which they are based on known facts ; but he does not 

 presume to urge the results on others. 



Finally, we have to examine how far the hypothesis 

 to which we have given the preference is confirmed by 

 the phenomena observable in entire muscles. The 

 tendonous covering on the ends of muscle-fibres may 

 be regarded as a layer of non-active conducting sub- 

 stance. In so far as the same phenomena are ex- 

 hibited in the uninjured muscle, as in the muscle- 

 prism or muscle-rhombus with its artificial cross 

 section, nothing need be added to the previous ex- 

 planations. But this is, as we have seen, though 

 generally, yet not always the case. The natural cross- 

 section of a muscle is generally very slight Ij^ negative, 

 sometimes not at all, as compared with the longi- 

 tudinal section ; but the negative character becomes 

 marked as soon as the natural cross-section has been 

 destroyed in any way, either mechanically, chemically, 

 ,or thermically. In explanation of this condition of 

 the natural ends of muscle-fibres, we may assume that 

 the arrangement of the molecules in the latter or in 

 the terminal muscle-elements in each muscle-fibre may 

 sometimes be different from that at all other points. 

 If, for example, the cross-section in the terminal 

 muscle-element were not negative, the muscle-fibre 

 could afford no current, though such a current would 

 arise as soon as this terminal muscle-element was re- 

 moved or was transformed into a non-active conductor. 

 E. du Bois-Reymond has lately succeeded in discover- 

 ing a very probable reason for this abnormal condition 

 of the ends of muscle-fibres ; but without entering too 



