DISSECTION OF THE DOG 99 



attached to the proximal part of the second phalanges of the second to fifth 

 digits. 



M. abductor digiti QuiNTi. — The abductor of the fifth digit is very rudi- 

 mentary and somewhat variable. Two parts can be distinguished : (1) In the 

 form of a tendinous band passing from the proximal part of the calcaneus to 

 the base of the fifth metatarsal bone ; (2) either with the same origin as the 

 first part, or as an offshoot therefrom, as a feeble fleshy belly continued by a 

 thin tendon to the first phalanx of the fifth digit. 



Dissection. — Cut across the short flexor close to its commencement ; cut 

 its connections with the fascia and turn it downwards as far as possible. 

 In performing this dissection care must be taken to preserve the two 

 plantar nerves — terminal branches of the tibial nerve — and the plantar 

 branch of the saphenous artery. 



M. flexor digttorum profundus. — The strong tendon of the m. flexor 

 hallucis longus runs along the groove on the calcaneus where it is bound down 

 by a strong annular ligament, and is joined by the much smaller tendon of 

 the m. flexor digitorum longus which has traversed a groove on the medial 

 malleolus. The powerful deep flexor tendon so formed divides into four parts, 

 one for each of the digits (second to fifth). Each tendon enters a flexor 

 sheath, pierces the ring formed by a tendon of the short flexor, and is finally 

 inserted into the terminal phalanx. 



Mm. lumbricales. — Three rather feeble lumbrical muscles arise from the 

 plantar surface of the deep flexor tendon. Their thin tendons are traceable 

 to the proximal end of the first phalanx of the third, fourth, and fifth digits. 

 Occasionally small tendinous slips may join one or more of the tendons of the 

 short flexor of the digits. 



M. quadratus PLANTiE. — The quadratus muscle is very small and thin, 

 and arises from the distal extremity of the calcaneus and the lateral collateral 

 ligament of the tarsus. Its fibres join the deep flexor tendon. 



N. tibialis. — The tibial nerve follows the tendon of the m. flexor hallucis 

 longus to a level with the joint between the tibia and the talus, where it divides 

 into the medial and lateral plantar nerves. 



The medial plantar nerve (n. plantaris medialis) is the smaller, and runs 

 along the medial border of the m. flexor brevis to the middle of the metatarsus, 

 where it ends in two branches. The more medial of the two is continued 

 onwards as the n. digiti plantaris communis I. The more lateral branch 

 crosses the plantar aspect of the short flexor muscle and divides into nn. meta- 

 tarsei plantares II, III, et IV, which join the common plantar digital nerves. 

 The lateral plantar nerve (n. plantaris lateralis) is much larger. Placed between 

 the superficial and deep flexor tendons, it disappears from view between the 

 origins of the most lateral interosseous muscle and the adductor of the fifth 



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