THE PUDENDAL PLEXUS. 1345 



The outer or lateral terminal branch (Fig. 1121) is larger than the inner and is situated 

 below the distal portion of the flexor brcvis digitorum and above the deep plantai fascia. After 

 a short forward course it splits into two branches, the lateral of which soon divides into two. 

 There are thus formed three plantar digital nerves (nn. digitales plantares communes), each of 

 which at the distal end of its metatarsal space divides into two digital nerves (nn. digitales 

 plantares proprii), the inner supplying the contiguous sides of the great and second toes, and the 

 middle and outer being distributed similarly to respectively the second and third and third and 

 fourth toes. The inner of the three sends a filament to the first lumbricalis, the middle some- 

 times to the second lumbricalis, while the outer forms an inosculation with the external plantar 

 nerve. In addition to innervating the muscles enumerated and the integument of the plantar sur- 

 face of the mesial three and one-half toes, each of the digital nerves sends tiny filaments toward 

 the dorsum for the supply of the nails and the tips of the toes. 



ee. The external plantar nerve (n. plantaris lateralis) (Fig. 1121) is a smaller nerve than the 

 internal and corresponds in its arrangement and distribution with the palmar branch of the ulnar 

 nerve. After separating from the internal plantar beneath the internal annular ligament, it 

 follows a course in company with the external plantar artery obliquely forward and outward 

 above the flexor brevis digitorum and below the flexor accessorius. Reaching the interval 

 between the abductor minimi digiti and the flexor brevis digitorum it divides near the head of 

 the fifth metatarsal bone into superficial and deep terminal branches. 



Branches of the external plantar, like those of the internal, include : collateral and terminal 

 branches. 



The collateral branches comprise muscular and cutaneous twigs. The muscular branches 

 are given off soon after the origin of the parent nerve ajid supply the flexor accessorius and the 

 abductor minimi digiti. The cutaneous branches are a series of small twigs which follow the 

 septum between the flexor brevis digitorum and the abductor minimi digiti and become super- 

 ficial by piercing the deep plantar fascia. They supply the integument of the lateral portion of 

 the sole. 



The terminal branches are : the superficial and the deep. 



The superficial or cutaneous branch (r. superficialis) inosculates with a branch of the 

 internal plantar and continues forward in the interval between the flexor brevis digitorum and 

 the abductor minimi digiti, eventually splitting into an external and an internal branch. 



The external branch (Fig. 1121) sends filaments to the flexor minimi digiti and the inter- 

 ossei muscles of the fourth metatarsal space, after which it becomes cutaneous near the fifth 

 metatarso-phalangeal articulation and continues forward as the plantar digital nerve for the 

 lateral aspect of the fifth toe. 



The internal branch (Fig. 1121) courses forward in the fourth metatarsal space, at whose 

 distal end it separates into two filaments which supply the opposed surfaces of the fourth and 

 fifth toes. The digital branches send filaments dorsally for the nails and the tips of the toes. 



The deep or muscular branch (r. profundus) accompanies the external plantar artery 

 in an obliquely forward and outward course above the adductor obliquus hallucis and the flexor 

 accessorius and below the interossei muscles. It forms an arch (Fig. 1121) whose convexity is 

 directed forward and outward, and terminates in the region of the base of the great toe. From 

 the convex aspect of the arch are given off the filaments which innervate the interossei muscles 

 of the first, second, third and sometimes the fourth interosseous space. Other muscular twigs 

 supply the adductores obliquus and transversus hallucis and the outer three lumbricales, the 

 branch to the second lumbricalis first passing beneath the adductor transversus hallucis. The 

 branches to all of these muscles enter their deep surface. In addition to the muscular distribu- 

 tion, articular twigs are furnished to the tarsal and tarso- metatarsal articulations. 



THE PUDENDAL PLEXUS. 



The pudendal plexus (plexus pudendus) is the downward continuation of the 

 sacral plexus, and, whilst each retains more or less its individuality as a distinct 

 structure, there is no sharp line of demarcation between the two. Considerable 

 interlacing and overlapping is the rule, so that often some of the important branches 

 of the pudendal plexus are derivatives to a large extent from the elements giving rise 

 to the sacral plexus. 



The pudendal plexus (Fig. 1122) is situated on the posterior wall of the pelvis 

 and is formed by contributions from the anterior primary divisions of the first, second 

 and third sacral nerves, from the entire anterior primary divisions of the fourth and 

 fifth sacral and from the coccygeal nerve. 



Communications. The nerves helping to form the plexus receive gray rami 

 communicantes from the gangliated cord of the sympathetic, which .join them shortly 

 after the nerves emerge from their intervertebral foramina. 



85 



