178 PROCEEDINGS OF THE ACADEMY OF [1894. 



aries to the great triceps on the other side of the femur aud to the 

 gastrocnemius. 



The arrangement and action of the thigh muscles are imitated by 

 the rubber bands of the small model (fig. 1). The up and down 

 stick represents the femur, the upper horizontal stick the pelvis, the 

 lower stick the upper end of the tibia. The rubber band from a to 

 c is the rectus femoris muscle, with a short leverage above and a long 

 one below. The rubber band from b to d is one of the croup muscles 

 Avith a greater leverage above than below. The simultaneous short- 

 ening of the muscles on botli sides of the femur throws, then, the pelvis 

 forward far and fast compared with the actual contraction in the lines 

 of the muscles themselves. 



To show how little this differential co-ordinate action of the muscles 

 and tendons has been understood, I shall quote a passage from 

 Chauveau.* 



Speaking of the tendinous portion of the flexor metatarsi he says : 



"Some have attributed to it still another use, that of passively 

 opposing itself to the flexion of the femur on the leg while standing, 

 and serving thus as an auxiliary to the muscular forces which hold 

 in equilibrium the weight of the body. This is wrong according to 

 us. For it to fulfil this function, the foot would have to be held in 

 a fixed situation by the contraction of its extensor muscles. Now 

 these muscles are indeed the gastrocnemii of the leg, which take 

 their origin behind the femur, aud which tend to flex this bone on 

 the tibia, that is to say, to cause the movement which they are sup- 

 posed to be charged to hinder. ' ' 



" Besides, experiment shows pretty well that we are right ; the cut- 

 ting of this tendinous cord, practised on the living animal, does not 

 change its appearance while resting on one or both hind legs." 



* " Ce tendon jouit de la curieuse propriete de plier le jarret par une action 

 toute mecanique, lors de la flexion des rayons superieurs du niembre. On lui 

 a encore attribue iin autre usage, celui de s' opposer passiveiuent ;\ la flexion du 

 femur sur la jamlie pendant la station et de servir ainsi d' adjuvant aux forces 

 musculaires qui font equilibre au poids du corps. C'est a tort, suivant nous. Pour 

 qu' elle (corde conductrice) piit remplir ce role, il faudrait que le pied fut main- 

 tenu en situation fixe par la coutractiou de ses muscles extenseurs. Or, ces 

 muscles sontjustement lesjumeaux de la jambe, qui preuuent leur origine en 

 arriere du femur et qui tendeut a op;' rer la flexion de cet os sur le tibia, c'est-a-dire 

 a determiner le mouvement qu' on les suppose charges d' empecher. L' experi- 

 mentation, du reste, montre assez que nous somraes dans le vrai: la section de 

 cette corde tendineuse, pratiquee sur 1' animal vivant, ne trouble nullement 

 I'habitude exterieure de celui-ci, ni pendaut la station libre. ni pendant la station 

 forcee." Chauveau. Traite d' Anatomic Comparee des Animaux domestiques. 

 Page 357. 



