270 ANATOMICAL TECHNOLOGY. 



the origin of the ex. -rad. longior. The origin area cannot be seen fully until after the 

 removal of the ex. communis. 



Insertion. — The tendon passes through the same groove as the tendon of the ex. rad. 

 longior, and is inserted upon the dorsal side of the proximal end of the medial metacarpal. 



M. EXTENSOR (DIGITORUM) COMMUNIS. 



§ 697. Synonymy. — The muscle has the same name in human anatomy, G,, A, 417, 

 Q., A, I, 216 ; extenseur commune des doigts, S. -D. , A, II, 364 ; extenseur anterieur des pha- 

 langes, Ch., A, 375 ; anterior extensor of the phalanges, Ch. (FL), A, 263 ; ext. dig. commu- 

 nis, Miv., B, 151. 



Figures. — Ectal aspect (74) ; origin area (68, 71). 



Dissection. — The muscles remaining upon the cephalic and dorsal surfaces of the ante- 

 brachium are covered by a dense fascia which must be removed. Near the wrist note a, 

 wide tendon which passes ectad of the M. abductor ossis metacarpi poUicis. Trace it to the 

 corresponding muscle, and this to the humerus, and transect the muscle at its middle. 



Origin. — By fleshy and tendinous fibers from the epicondylar ridge. The origin area 

 is about 9 mm. long, and extends from the disto-cephalic angle of the origin area of the 

 cephalic division of the entotriceps to the trochlea ; it lies just dorsad of the origin area of 

 the extensor rad. brevior and of the distal fifth of the ex. rad. longior. 



Insertion. — The tendon lies in a groove upon the dorsal surface of the distal end of the 

 radius, from which it may be disengaged by slitting up the ligament which converts the 

 groove into a canal. It then divides into four tendons which may be traced to the dorsal 

 aspect of the four ordinary digits. 



M. EXTENSOR MINIMI (DIGITI). 



§ 698. Synonymy. — The human muscle so called (G., A, 417, .Q., A, I, 218), sends a 

 tendon to only the minimus, while in the cat and dog what seems to be the same muscle 

 supplies also the annularis and medius ; (see Huxley, A, 418). S.-D., however (A, II, 368, 

 369), regards it as forming three separate muscles, one for each digit, excepting the pollex 

 and index, which he terms Ex. prop, du verpus, paramese and micros, respectively. Exten- 

 seur laterale des phalanges, Ch., A, 279 ; lateral extensor of the phalanges, Ch. (PI.), A, 264 ; 

 extensor minimi digiti, Miv., B, 151. 



Figures. — Dorsal aspect (74) ; origin area (68, 71). 



Origin. — From the ventral border of the epicondyle just distad of the origin of the 

 extensor communis. The proximal part of the origin is by muscular fibers, and the distal 

 by a short tendon At 2-3 mm. from the origin the muscle divides into a slender ectal 

 portion and a thicker ental part, which are in close contact, but may be separated witbout 

 cutting fibers. The former becomes tendinous at the junction of the proximal and middle 

 thirds of the antebrachium, and the latter at the junction of the distal and middle thirds. 



Insertion. — The tendons join the corresponding tendons of the extensor communis. 



M. EXTENSOR (CARPI) ULNARIS. 



§ 699. Synonymy. — The human muscle of the same name, G., A, 417, Q., A, 1, 318 ; 

 cvMtal, S.-D., A, II, 860 ; ex. carpi ulnaris, Miv.. B, 153. 



Figures. — Dorsal aspect (74) ; origin area (68). 



Origin. — In two parts : (A) by a short, broad tendon from the distal end of the epicon- 

 dyle next to the origin of the extensor minimi ; (B) by a smaller and rounded tendon 

 from the proximal lip of the sigmoid notch of the ulna. 



