IRREGULAR MUSCLE-RHOMBl. 197 



the lono-itadinal, as on the cross-sections, is situated in 

 the centre, and an arrangement of the tensions exactly 

 similar to that in a muscle-prism is observable. 



From what has been said, the direction and strength 

 of the currents which are generated on the intercon- 

 nection of any points in a muscle-prism by the appli- 

 cation of an arch may easily be inferred. They are 

 represented in fig. 53. The direction of the currents 

 in the applied arches is in every case indicated by 

 arrows ; where there are no arrows the arch connects 

 two points of equal tension, so that there is no current 

 (e.g. arches 4 and 9). The currents all pass from the 

 obtuse to the acute angle, through the applied arches, 

 except in the fifth and tenth, in which the direction is 

 reversed. 



4. The phenomena in irregular muscle-rhombi do 

 not differ essentially from those just described, but the 

 arrangement of the tensions is asymmetrical. Passing 

 to muscles in which the arrangement of the fibres is 

 irregular, it is apparent that each cut made must always 

 meet a part of the fibres obliquely, and that, therefore, 

 the matter just explained must always be borne in mind 

 in explanation of the phenomena, which are sometimes 

 very complex. Not to enter too far into details, we 

 need only say that the same fundamental principle 

 asserts itself in all muscles ; everywhere the longi- 

 tudinal section, as distinguished from the cross-section, 

 is positive ; and in all cases there is a point or line in 

 the longitudinal section which is the most positive, 

 and a point in the cross-section w^hich is most negative ; 

 so that, if an arch is applied, currents pass through this 

 from the longitudinal to the cross-section, weaker cur- 

 rents between points in the longitudinal section, and 



