170 LABORATORY MANUAL OF HUMAN ANATOMY 



the turning of the tendo calcaneus [Achillis] downward. Deter- 

 mine its insertion. It is the homologue of the palmaris longus in 

 the forearm. In monkeys, whose feet are prehensile, it is the 

 proper tensor muscle of the plantar fascia. It is well developed 

 in all plantigrade animals. 



Deep Transverse Fascia of Leg and Structures beneath it. 



Note its attachment medially to the tibia and laterally to the 

 fibula. Trace the fascia downward to the ankle, where it becomes 

 thickened to form the ligamentum laciniatum (0. T. internal an- 

 nular ligament). (Vide Spalteholz, Fig. 395.) Incise this fascia 

 longitudinally, leaving the Lig. laciniatum intact, and proceed to 

 the study of the structures beneath it. 



Muscles. Note carefully the form, position, origin, insertion, action, and 

 innervation of each. (Vide Spalteholz, Fig. 395.) 



(a) Popliteus muscle (M. popliteus). Determine the relation of its 



tendon to the capsule of the knee-joint and the ligamentum pop- 

 liteum arcuatum. Note the dense aponeurosis covering this 

 muscle. It receives a strengthening band from the tendon of the 

 semimembranosus muscle. Examine the bursa of the popliteus 

 muscle (bursa M. poplitei}. (Vide Spalteholz, Fig. 396.) Does 

 this bursa communicate with the knee-joint? 



(b) Long flexor of the digits (M. flexor digitorum longus). (Vide 



Spalteholz, Fig. 395.) Examine the sheath of the long flexor 

 tendons of the toes (vagina tendinum M. flexoris digitorum pedis 

 longi). This sheath surrounds the tendon as it passes behind the 

 malleolus medialis and is continued well down into the foot. 

 Does it communicate with a sheath which surrounds the tendons 

 of the tibialis posterior and the flexor longus hallucis? 



(c) Posterior tibial muscle (M. tibialis posterior] (0. T. tibialis pos- 



ticus). This muscle may be more or less fused with the long 

 flexors, which is only an exaggeration of the normal disposition 

 in man and a reproduction of the normal disposition in the cat. 

 ( Strauss-Diirckheim. ) 



Examine the sheath of the tendon of the M. tibialis posterior 

 (vagina tendinis M. tibialis posterioris) . 



(d) Long flexor of the great toe (M. flexor hallucis longus). Examine 



the sheath of the tendon of the long flexor of the great toe 

 (vagina tendinis M. flexoris hallucis longi). 



At this stage in the dissection examine the bony leg and foot. 

 Determine the exact position of the sulci through which these 

 tendons pass. Note the exact relation of the tendons beneath 

 the ligamentum laciniatum. (See Fig. 71.) 



Varieties in the flexor system of the foot are frequent. The 

 tendency to differentiate may be accentuated, but more fre- 

 quently there is a return to the primitive undivided mass arising 



