358 



quiry into the advantageous disposition of the articulation of the foot 

 with the leg, for facility in walking, and in the different motions of pro- 

 gression. 



We have seen that the tendons are generally inserted at a very acute 

 angle, into the bones on which they act; in the present instance, however, 

 the insertion takes place at aright angle, the common tendon of the mus- 

 cles of the calf of the leg joining the os calcis, at the angle most favour- 

 able to their freedom of action. With the exception of the muscles 

 which move the head and lower jaw? no others are so evidently disposed 

 with this purpose. Nature has not been contented with forming the foot 

 in such a manner as to afford the most advantageous lever, to which the 

 moving powers are applied, at the greatest possible distance from the 

 fulcrum, and at the angle most favourable to their action; she has further 

 increased the efficacy of this action, by adding extraordinarily to the 

 number of muscular fibres. There is not, in the body, a stronger mus- 

 cle than the soleus, whose short and oblique fibres between the two wide 

 aponeuroses which cover its anterior and posterior surfaces, are more 

 numerous than in any other muscle, as may be conceived, by consider- 

 ing the extensive surfaces to which they are attached. Besides, the ten- 

 do Achillis is kept in a due degree of straightness, by the aponeurosis of 

 the leg behind it. 



Every thing in the powers, as well as in the levers, is formed so as to 

 overcome the resistance, without difficulty; that is, so as to raise the 

 weight of the body, by the extension of the foot, the end of which rests 

 on the ground in every motion of progression. 



This immense power with which the muscles of the calf of the leg act 

 to raise the heel, and to support the whole weight of the body resting on 

 the astralagus, accounts for the possibility of transverse fractures of the 

 os calcis, and for the rupture of the tendo Achillis, notwithstanding its 

 great thickness ; and should lead one not to allow patients, after such ac- 

 cidents, to walk freely, for several months; the substance which unites 

 the parts being liable to rupture, as is known to have been the case in 

 several instances. This same arrangement of parts likewise accounts for 

 an accident, which physiologists have long endeavoured to explain by a 

 very unsatisfactory theory. 



It not unfrequently happens, that the mere effort of walking occasions 

 a rupture of some of the fibres of the gemelh and of the soleus. in conse- 

 quence of which there comes on pain, attended with induration of the 

 muscles, and with a certain degree of ecchymosis, occasioned by the ex- 

 travasation of blood. Pathologists suppose these symptoms to depend on 

 a rupture of the plantaris muscle: this rupture, however, is hypothetical, 

 has never been proved by experience to exist, and its supposed symptoms 

 are altogether idle and fallacious. 



I could, if it were not out of place, bring forward several cases of this 

 affection : in all the cases which have come under my own observation, 

 the use of the bath, of emollient and slightly narcotic poultices, but above 

 all, continued rest, while the symptoms lasted, have appeared to me the 

 most appropriate remedies. 



CLXXXVIII. Of running. In running, the foot that is hindmost 

 being raised before that which is foremost, being firmly applied to the 

 ground, the centre of gravity is, for a moment, suspended, and moves iu 

 the air, impelled by the force of projection, the action of which princi- 

 pally constitutes leaping. 



