The deep branch of lateral plantar nerve (muscular branch) accompanies the lateral plantar artery on the deep surface of the tendons of the Flexor muscles and the Adductor hallucis, and supplies all the Interossei (except those in the fourth metatarsal space), the second, third, and fourth Lumbricales.
This article incorporates text in the public domain from page 963 of the 20th edition of Gray's Anatomy (1918)
