40 



across every second change of C which primarily 

 act in connection with the originating movement, 

 or winding line formed by the leading point of ap- 

 pHcation. The intermediate planes do not become 

 planes of pressure until the movement of the sub- 

 sidiary point of appHcation [^. e., not the leading 

 point] affects the cross-lines. For this and for 

 other reasons, we find it more convenient to treat 

 of the planes at the commencement and ending of 

 S S as containing points of application. 



§ 42. The winding lines from the head having 

 been formed, and a succession of heUcal turns 

 shaped against the passive resistance of the succes- 

 sive posterior points of application, then active 

 counter-action begins from the rearmost of these 

 latter points, and its effects are transferred forward 

 from point to point, actually estahlisJiing first in the 

 anterior cross-line, and then in each succeeding 

 cross-line the latent reversal of their respective S S. 



The whole force is thus centred on the head, and 

 when this, by its actual or relative movement, re- 

 leases the front point of aj^plication, the winding 

 line from the rear point cutting, as it were, through 

 the body of the snake, allows the development of the 

 spring, and becomes, on the opposite aspect of 

 each C, the new alternating anterior winding line. 



