i;8 M-ufcles of the "[Book IX. 



The extenfors of the whole hand are, 

 The extenfor carpi radialis longior, which arifes 

 from the lower part of the external ridge of the os hu- 

 meri, above its external condyle. Ic is inferted into 

 the upper part of the metacarpal bone, which fupports 

 the fore-finger. Its efFeft is to extend the writ! and 

 draw the hand backwards. 



The extenfor carpi radialis brevior arifes from the 

 outer part of the external condyle of the humerus, and 

 from the ligament which connects the radius to it. It 

 is inferted into the upper part of the metacarpal bone of 

 the middle finger, and extends the wrift. 



The extenfor carpi i?lnaris arifes from the external 

 condyle oftheos humeri, and alfo receives an acceflion 

 of fibres in its progrefs from the ulna. Its round ten- 

 don is confined by a membranous Iheath in a groove, 

 which is fituated at the extremity of the ulna. It is 

 inferted into the upper part of the metacarpal bone of 

 the little finger, and affifts in extending the wrift. 

 The flexors and extenlors of the four fingers are, 

 The flexor fublimis perforatus, which arifes from the 

 internal condyle of the os humeri, the inner edge of 

 the coronoid procefs of the ulna, and the upper and 

 anterior part of the radius. It fends off four tendons 

 before it pafies under the ligament of the wrift, which 

 being divided for the pafiage of the tendons of the 

 following mufcle, are inferted into the anterior and up- 

 per part of the fecond bone of each finger. It bends 

 the fecond joints of the fingers. 



The flexor profundus perforans, which originate! 

 from the upper part of the ulna, and from a confiderable 

 part of the interofleous ligament. It divides into four 

 tendons, which pafs through the ilits in the tendons 

 of the preceding mufcle, and are inferted into the up- 

 9 PW 



