190 rilYHDl.MiiY OF MfSCLFS AND NKKVF>. 



parallel to cadi other, and that the l\vo ruts are made 

 at right angles to the direction of the fibres. Yig. 4! 

 diagrammatically represents a regular muscle-prism of 

 this sort. Tin- horizontal stripes represent the separate 

 bundles of the fibres. The outer surface of the prism, 

 \vhich therefore corresponds with the upper surface of 



the fibres, is c;dle<l the liHij/itiK/iinll xi'i-tiuii of the 



p/ism ; and the terminal surfaces, at right angles to 

 the Longitudinal section, are the < /v>.sN-.svr//'o//x of the 

 muscle-prism. The lines running at right angles to 

 the direction of the fibres are, as \ve >hall presently 

 find, tension-curves. 



A regular muscle-prism such as this exhibits a very 



'' a' n' a' ,i n' a' a' a' a' 



IM<; -10. A i:i:<a I..M: Mrst I.I:-PI:I>.V, 



simple distribution of tension. All the lines of tension, 

 or the iso-eleetric curves, run on the surface and are 

 parallel to the cross-sections. Kound the middle of the 

 muscle-prism passes a line separating it into two sym- 

 metrical halves; this \\ e will call the equator. The 

 jri'iiti-xt jiox'it'ii-i' li'usinii to be found anywhere on the 

 surface prevails at this point. Kvery point on the 

 equator has a greater positive tension than any other 

 point on the longitudinal, or the cross-section. On 

 either side from the equator, the posit i\e tension gra- 

 duallv decreases along the longitudinal section quite 

 r-gularly in both direction-, until, at the point \\hen- 

 the longitudinal meets the cro eetion, i! =(). 



D 



On the cross-sections themselves the tension is 



