121. =Anterior tibial artery.=--The anterior tibial artery comes in front of the interosseous membrane, one inch and a quarter below the head of the fibula, and here lies close to this bone. Its subsequent course is defined by a line drawn from the front of the head of the fibula to the middle of the front of the ankle. This line corresponds pretty nearly with the outer border of the tibialis anticus all the way down. If this muscle be put in action, its outer border (the intermuscular line) is plainly seen, and the incision for the ligature of the artery in any part of its course may be defined with the greatest precision. The artery can be felt beating and can be compressed where it crosses the front of the tibia and ankle. 122. =Posterior tibial artery.=--The posterior tibial commences about one inch and a quarter below the head of the fibula. Its subsequent course corresponds with a line drawn from the middle of the upper part of the calf to the hollow behind the inner ankle, where it can be felt beating distinctly about half an inch behind the edge of the tibia. A vertical incision down the middle of the calf would reach the artery under cover of the gastrocnemius and soleus. A vertical incision along the middle third of the leg, about half an inch from the inner edge of the tibia, would enable the operator to reach the artery sideways, by detaching from the bone the tibial origin of the soleus. 123. =Saphena veins.=--The subcutaneous veins on the dorsum of the foot form an arch convex towards the toes (as on the back of the hand), from which issue the two main subcutaneous trunks of the lower limb, the internal and external saphena veins. The internal saphena vein can be always plainly seen over the front of the inner ankle. Its further course up the inner side of the leg, knee, and thigh to its termination in the femoral is not in all persons manifest. The external saphena vein runs behind the outer ankle and up the middle of the calf to empty itself (generally) into the popliteal vein. _THE FOOT._ What are the bony landmarks which guide us in the surgery of the foot? 124. =Points of bone.=--Along the inner side of the foot, beginning from behind, we can feel--1, the tuberosity of the os calcis; 2, the projection of the internal malleolus; 3, the projection of the os calcis, termed ‘sustentaculum tali,’ about one full inch below the malleolus; 4, about one inch in front of the malleolus internus, and a little lower, is the tubercle of the scaphoid bone; the gap between it and the sustentaculum tali being filled by the calcaneo-scaphoid ligament and the tendon of the tibialis posticus, in which there is often a sesamoid bone; 5, the internal cuneiform bone; 6, the projection of the first metatarsal bone; 7, the sesamoid bones of the great toe.