DISSECTION OF THE DOG 89 



cutaneous nerve (n. cutaneus dorsalis medialis) to the first digit, and then the 

 second, third, and fourth dorsal digital nerves (nn. digitales dorsales II, III, et 

 IV) which accompany the corresponding arteries. 



N. peron^us profundus. — The deep peroneal nerve cannot be satisfactorily 

 followed at the present stage of dissection, but may be found lying medial 

 to the tendons of the long extensor muscle at the distal end of the tibia. A 

 large artery, the a. dorsalis pedis, runs medial to the nerve. 



Fascia. — The deep fascia on the lateral aspect of the leg is thick, especially 

 in the proximal part of the region where it is connected with the aponeurotic 

 tendon of the biceps muscle. Close to its attachment to the anterior border 

 of the tibia, longitudinal fibres give strength to the fascia. Intermuscular 

 septa are projected between the several muscles of the region. 



In the distal third of the leg the tendons of the anterior tibial muscle and 

 the long extensor of the digits are bound to the tibia by a band-like specialisa- 

 tion of the fascia, known as an annular ligament. One end is attached to the 

 tibia, the other to the line of union of the two bones of the leg. 



Two other annular ligaments occur in the front of the tarsus. One binds 

 down the tendon of the extensor digitorum longus. The other, at the same 

 level, is provided with two compartments ; one containing the tendons of the 

 extensor digiti quinti and peronseus brevis, the other the tendon of the peronseus 

 longus. Yet another annular ligament fixes the tendon of the peronseus longus 

 muscle in the groove on the lateral malleolus. 



The muscles in the region now being examined are seven in number, namely : 

 mm. tibialis anterior, extensor digitorum longus, peronseus longus, extensor 

 digiti quinti, peronseus brevis, extensor hallucis longus, and extensor digitorum 

 brevis. 



M. tibialis anterior. — The anterior tibial muscle, as its name indicates, 

 lies in front of the tibia, and is the largest and most medial of the group of 

 muscles in this region. Its origin is from the lateral condyle (a small origin) 

 and the lateral surface of the anterior crest of the tibia. About the junction 

 of the middle and distal thirds of the leg a rounded tendon begins, and, passing 

 under the annular ligament, crosses the tarsus obliquely to be inserted into 

 the rudimentary first metatarsal bone (or the proximal end of the second 

 metatarsal bone). 



M. extensor digitorum longus. — The long extensor of the digits lies 

 partly under cover of the anterior tibial muscle and partly to its lateral side. 

 It takes origin by means of a rounded tendon from a rough depression between 

 the lateral condyle and the patellar surface of the femur. Running down 

 a groove between the lateral condyle and the tuberosity of the tibia, the muscle 

 lies on the surface of this bone. In the distal third of the leg the fleshy belly 

 gives place to a strong round tendon, which, passing under the annular ligament, 

 divides into four parts at the tarsus. These are finally inserted into the terminal 

 phalanges of the digits. Each tendon becomes expanded over the metatarso- 



