PLATE XXXIV. 



SUPERFICIAL VIEW OF THE SOLE. FIRST LAYER 



OF MUSCLES. 



In this plate the first layer of muscles of the sole is shown, the skin having been 

 reflected. The thick tough subcutaneous tissue which lies beneath it has been removed, 

 and the central portion of the plantar fascia divided ; the posterior portion, from which 

 the flexor brevis digitorum arises, has been left in situ, while the anterior portion has 

 been reflected. The plantar fascia, like the palmar, is divided into three portions, two 

 lateral, which are thin and cover the abductores hallucis and minimi digiti respectively, 

 and a central one, which is very thick and strong, extending from the os calcis behind 

 to the toes in front, and sending down two intermuscular septa which completely shut 

 off the flexor brevis from the abductors of the hallux and little toe. In front this 

 central portion divides into five slips, and after sending a few median fibres along each 

 toe to join the superficial fascia, each slip splits opposite the metatarsophalangeal joint 

 into two, which pass down to be inserted on either side of the corresponding flexor 

 tendons into the glenoid plates and deep transverse ligament. Each slip is thus 

 perforated by the flexor tendons, while between the slips the digital nerves and artery 

 pass to the respective toes. The fascia was originally the expansion of the tendon of 

 the plantaris, which is very large in many mammals, and supplies the perforated flexor 

 tendons to the toes, in some species even running on past the first phalanx to be 

 connected to the second. Owing, however, to the outgrowth of the heel and the 

 pressure upon it, the two parts have become entirely separated, differing in this respect 

 from the palmaris longus, which is still connected with its expansion the palmar 

 fascia. 



The first layer of muscles consists of three : 1. Abductor hallucis ; 2. Flexor 

 brevis digitorum ; 8. Abductor minimi digiti. To these is sometimes added another, 

 which is called the abductor ossis metatarsi quinti, or Wood's muscle. It is not always 

 present, but when absent as a muscle it is represented by a band of fibrous tissue 

 passing from the tubercle of the fifth metatarsal bone to the outer tubercle of the os 

 calcis. 



The flexor brevis digitorum is represented in the plate as having only three 

 tendons. This is a common condition, but it more often has a fourth tendon to the 

 little toe ; and when this exists it is slender and weak. 



In some cases the superficial digital branch of the internal plantar artery (c) 

 anastomoses with a branch from the external, and thus forms a superficial plantar arch ; 

 while the twigs given off from it pass towards the cleft of the toes, and anastomose with 

 the digital branches of the deep arch. Thus it is analogous to the superficial palmar 

 arch. 



