u />/./> / /'// /: . i \ rr.u i< > it i. IMUS. 259 



tin .decranon, after receiving a great number of fibres from tho short extensor, 

 and after gliding, by means of a synovial capsule, over the eminence which 

 s for its insertion. 



1\> lotion*. The external surface is covered by a thin, fibrous, white-and- 

 yellow clastic layer, which separates it from the panniculus; it is hollowed, 

 mar tin- upper bonier of the muscle, by an excavation into which is received 

 the posterior portion of the long abductor. Its internal face responds to 

 the grout dorsal, the adductor of the arm, and to the long extensor. Its posterior 

 border is margined by the latter muscle ; tho superior follows the axillary 

 Imrdcr of tho scapula, and is attached to it to constitute the fixed insertion 

 of the muscle ; the inferior responds to the short and middle extensors. 



Action. It is an extensor of the fore- arm. 



3. Short Extensor of the Fore-arm. (Fig. 119, 8.) 



Synonym* Humero-oleoranius cxternus - Girurd. The vastus externus of the 

 triceps bmchiolis of Man. (Caput medium Percitatt.) 



Situation Direction Form Structure. This muscle is situated 

 betwe< n the humerus and the inferior border of the preceding, and is 

 directed obliquely downwards and backwards. It is thick and short, 

 flattened and apoueurotic at its upper extremity, prismatic, and entirely 

 formed of thick parallel muscular fasciculi for the remainder of its extent. 



Attachments. One of its attachments is on the humerus, to the cu/vc-.d 

 line extending from the deltoid imprint to the base of the articular head 

 (see for this line Fig. 41, above 4), by the short aponeurosis of its superior 

 extremity fixed insertion ; the other is to the olecranon, either directly, or 

 through the tendon of the large extensor- movable insertion. 



Relations. The prismatic shape of this muscle offers three faces, which 



aid : externally, to the two abductors of the arm and to a slight fibrous 



continuous, above, with that which covers tho large extensor, and below, 



with tin- antibrachial aponeurosis ; internally, to the small extensor, from 



uliicli it is difficult to separate it, to tho short flexor of the fore-arm, and to 



the anterior extensor of the metacarpus; superiorly, to the large extensor, 



which dnsr-ly adheres to it. 



it. An extensor of the fore-arm. 



4. MiJdle Extensor of the Fore-arm. (Figs. 119, 17 ; 121, 8.) 



Synonym*. llmm ro-oWruninrt interims Gininl. Tin- va iu~ internus of the 

 triceps brut-Ilia!!." <! Man. (( 'n^itt parrum 1'in-iniU.) 



(ion Direction Form Structure. This muscle is situated nt 



the internal face of the humerns, along the inferior border of the large 



It is oblique downwards and backwards, pyriform, bulging at its 



rior extremity, contracted infericrly, wh. re it terminates by two small 



flat tendons. 



Alt", -I, n,<nt8. It originates, by its superior extremity, from tho inner 



aspect of the humerus, behind and above tho tubore.sity on its body. Ono 



. luiiml tendons is attached to the summit <>f the olecranon. the 



tiler glides over a small c< nvexity on lli. inner > ; de . t' that emim nee, and 



goes to be inserted a little lower than the first. 



<;/x. Above, with the inferior border of the largo cxUnsc.i ; otit- 

 wards. with the humerus. the short hYxor, and short \t< II.-T of the for. - 

 arm ; inwards, uith the humeral iiix. rti"ii of the great .1 >r>.il and the 

 adductor of tin- arm. the l-.ng hrum-h of tl'O coiaco-l.iaehialis. tho vessels 



S 2 



