DISSECTION OF THE UPPER EXTREMITY 103 



Mm. lumbricales. Study origin, insertion, form, position, action, 

 and innervation of each of the four lumbrical muscles. Divide 

 the M. flexor digitorum profundus in its muscular part in the 

 forearm and reflect it far distalward, along with the Mm. lum- 

 bricales. Take this opportunity to secure the branches of the 

 ramus profundus of the ramus volaris manus of the N. ulnaris 

 supplying the two (ulnar) lumbrical muscles. 



Short Muscles of Thumb and Little Finger. 



Study carefully the form, position, origin, insertion, action, 

 and innervation of each of the following muscles : 



(a) Short abductor muscle of thumb (M. abductor pollicis brevis) (0. T. 



abductor pollicis). 



(b) Abductor muscle of little finger (M. abductor digiti quinti). 



(c) Short flexor muscle of little finger (M. flexor digiti quinti brevis). 



(d) Opposing muscle of thumb (M. opponens pollicis). 



(e) Short flexor muscle of thumb (M. flexor pollicis brevis). 



(f) Adductor muscle of thumb (M. adductor pollicis). 



(g) Opposing muscle of little finger (M. opponens digiti quinti). 



Deep Ramus of Volar Ramus of the Hand from the Ulnar Nerve (R. 

 profundus R. volaris manus N. ulnaris). 



Study- 



(a) Muscular rami (rami musculares) to all muscles of palm lying ulnar- 

 ward from tendon of M. flexor longus pollicis (except two radial 

 Mm. lumbricales). 



Deep Volar Arch (Arcus volaris profundus) (O. T. Deep Palmar 

 Arch). (See Fig. 34.) 



How is it formed! (Cf. Spalteholz, Fig. 460.) Compare its 

 convexity with that of the superficial volar arch. With a colored 

 pencil indicate its position on your own palm. Study carefully 

 its relation to neighboring muscles and nerves. Cut through the 

 M. adductor pollicis at its origin and reflect it. Follow out care- 

 fully each of the four following branches : 



(a) Volar metacarpal arteries (Aa. metacarpeae volares). 



(aa) A. metacarpeae volaris I. 



(aaa) Branch to thumb (0. T. arteria princeps pollicis). 



(aab) Branch to radial side of index-finger (0. T. arteria 



radialis indicis). 



(ab) A. metacarpea volaris II. (0. T. first palmar interosseous), 



forward between second and third phalanges to join A. 

 digitalis communis. 



