264 



that in the regular change of curvatui-es the convex 

 must pass over the concave ; that is, it must, in the 

 reduction, follow the direction of the line which 

 formed it. This line was, in the present case, the 

 secondary section of the left anterior Hne, whose 

 convex would pass over and to the left. If, in so 

 doiQg, it developed the corresponding section of the 

 right anterior line, that convex passing to the right 

 would oppose it. But it will, we think, be appar- 

 ent that the pressure of the rein reduces only the 

 lateral development of the convex, and, so far as 

 the perpendicular development is concerned, has 

 rather the contrary effect. Hence, it will he the 

 primary section of the alternate (right) posterior Utw 

 which pressure of the left rein on the left convex of the 

 loiuer G of the neck will develope. 



Again, the S being formed by the counteractions 

 of two forces, compounded each of an element of 

 pressure and an element of rotation, it may, we 

 think, be assumed that the pressure elements give 

 the longitudinal thrust, whereas the rotary element 

 in each secondary section gives an outward sideway 

 movement to the ribs, legs, and other parts dependent 

 on the convexity, 'whether this last be formed or only 

 forming. 



Connected with a primary section, the leg is car- 



