6o THE PRINCIPLES OF MYODYNAMICS. 



43. The hand lever is in myodynamic relation 

 with the bones of the fore-arm through the 

 muscles that span the wrist-joint. These mus- 

 cles may be divided into four groups. 



(i.) An aiiterior group Q,ox\\,2Axivi\<g the palmaris 

 longus, the flexor carpi radialis, the flexor carpi 

 ulnaris, the flexor sublimis digitorum, the flexor 

 longus pollicis, and the flexor profundus digi- 

 torum. 



(2.) An oiitward group containing the extensor 

 carpi radialis longior, the extensor carpi radialis 

 brevior, the three extensors of the thumb, and 

 the flexor carpi radialis. 



(3.) A posterior group containing the two 

 carpo-radial extensors, the extensor carpi ul- 

 naris, the extensor conmumis digitorum, the ex- 

 tensor minimi digiti, the extensor indicis, and 

 the three extensors of the thumb. 



(4.) An imvard group containing the flexor 

 carpi ulnaris and the extensor carpi ulnaris. 



(5.) The muscles of the anterior group flex, 

 those of the outward group abduct, those of the 

 posterior group extend, and those of the inward 

 group addtict the hand. 



