POSTERIOR MEMBER. 



305 



terior, which are always more vertical to the fetlocks. An inclina- 

 tion of 45 degrees is not observed in well-formed horses provided 

 with good axes ; it constitutes, on the contrary, a low-jointedness quite 

 marked. 



Let us now see the disadvantages which accrue from an^excess or 

 an insufficiency of 

 obliquity ; they are 

 of the same nature 

 as those which fol- 

 low an excess or 

 an insufficiency of 

 length. There are 

 several ways of ex- 

 plaining this : 



Let us first re- 

 gard the pastern as 

 an inclined plane 

 of surface and of 

 segment in the de- 

 composition of 

 forces parallel to 

 the weight. 



Suppose OS 

 and OD (Fig. 103) 

 are two pasterns 

 of the same length, 

 but unequally in- 

 clined upon the 



canon OC. From the fact of this inclination, the weight of the body, 

 which we will represent in quantity and direction by the line OR, is 

 decomposed, at the level of the fetlock O, into two forces, one of 

 which is parallel to the phalangal region, and is overcome by its own 

 resistance ; the other is perpendicular to the preceding. The latter is 

 exerted upon the sesamoid bones, and tends to lower the angle of the 

 fetlock against the summit of which the tendons are applied. 



These two components of the resultant OR are, by constructing the parallelo- 

 gram of forces : for OB, Oe and Of; for OD, Og and OD. They indicate, for 

 each inclination, the role which is intrusted to the bones and the muscles. The 

 sole inspection of the figure shows that with the pastern OB (straight-jointed), 

 the component Of exceeds Oe, and therefore likewise OD, which corresponds to 

 it in the other case. 



20 



FIG. 103. 



