ii MECHANICS OF LOCOMOTOE APPARATUS 113 



tarsal bones. Owing to the strength of the plantar ligaments 

 the arch of the foot can carry heavy weights without giving way. 

 Flat foot, owing to abnormal relaxation of these ligaments, is un- 

 favourable to the maintenance of equilibrium in the erect posture 

 and in walking. 



Owing to the formation of the skeleton and the arrangement 

 of its ligaments, the erect posture can therefore be maintained 

 with a comparatively slight expenditure of muscular energy. 

 But when it is necessary to remain standing for a long time, 

 an asymmetrical posture is generally preferred, in which the 

 main part of the weight of the body is thrown on one leg, while 

 the other is held in a forward and semi-flexed position. 



Vierordt, by an extremely simple graphic method, registered 

 the oscillations of the head in different positions, with the object 

 of determining the most natural posture, i.e. that which induces 

 the least fatigue and provides the greatest stability of the body. 

 The method consisted in attaching a pen to the head by a suitable 

 cap, which traced on a paper fixed horizontally from above the 

 oscillations of the principal axis of the body in different postures, 

 each being maintained for three minutes. He found that the 

 antero-posterior and lateral oscillations are considerably greater 

 in the symmetrical military posture than when the weight was 

 thrown upon one leg (asymmetrical). The latter posture is 

 accordingly the most natural, and preference is given to it in 

 sculpture and painting. 



According to Vierordt the advantages of the asymmetrical 

 posture are as follows : 



(a) Greater rigidity of the hip- and knee-joints, due to almost 

 the whole weight of the body falling on the limb which serves 

 as support ; this produces increased tension of the ligaments, 

 particularly of the ileo-femoral. 



(&) The calf muscles of only one side are active, and less 

 work is thrown upon these than in the symmetrical posture. 



(c) The advanced limb, which does not bear the weight of the 

 body, exerts a slight pressure on the ground, so that when the 

 quadriceps extensor of the knee comes actively into play to hinder 

 the body from falling forwards, it works under favourable con- 

 ditions. In the symmetrical posture, on the contrary, the calf 

 muscles on both sides work under a heavy load to attain the 

 same end. 



(d) The appreciation of pressure by the sole of the advanced 

 limb, and the muscle sense generally, are under the most advan- 

 tageous conditions in the asymmetrical posture, so that oscillations 

 of the centre of gravity are more readily perceived, and promptly 

 compensated by muscular reaction. 



And, as in the asymmetrical attitude, the muscles of one 

 limb only become fatigued, it is possible to remain longer 

 VOL. Ill I 



