POSTERIOR MEMBER. 



301 



This view, too absolute in its character, has been recently opposed 

 by our colleague, M. Pader,^ who has pointed out with reason the 

 articulation of the foot — that is to say, the last inter-phalangal artic- 

 ulation, and not the hoof — as the centre of the movements of rotation 

 of the phalangal lever upon the soil. 



This statement being made, the phalangal segment may be repre- 

 sented schematically, during station, by the angular lever AOB (Fig. 

 99), which rests by its point, 

 B (fixed point), upon the 

 third phalanx, and receives 

 at O (fetlock) the weight of 

 the body, OR, transmitted 

 through the canon, OC. 



The muscular action, 

 M, exercised upon the sesa- 

 moid bones. A, must there- 

 fore, at each instant of the 

 contact, in order to main- 

 tain the equilibrium, an- 

 tagonize the force, R, and 

 counterbalance it, so that 

 the fetlock, O, where it is 

 applied, may remain in its 

 normal situation. 



Let us now draw, from the 

 point of support, B, the per- 

 pendiculars BF and BE upon 

 the direction of the two forces, 

 M and R ; these lines, it is 

 seen, are the respective lever- Fig. 99. 



arms of each of these forces, 



and it will be seen that here, as in all levers of the second class, the arm, BF, of 

 the power overcomes that, BE, of the resistance. 



It is known, besides, that a lever is in equilibrium when the movements of 

 the two forces are equal. 



Whence, since equilibrium does exist, we have the following formula : M X 

 BF (mom. of the force M) = RXBE or IH (mom. of the force K). 



This being laid down, let us now lengthen the pastern, and make it OD, for 

 example. 



The new arms of the lever will he DG and DI. Both will be lengthened by 

 the same quantity, HD, which will necessarily disturb the equilibrium, for the 

 arm of resistance will have augmented, relatively, by a greater quantity than that 



• Pader, De la ferrure normale, in Bulletin de la Soc. cent, de mi?d., vOt. annee, 1888, p. 497. 



