b. Muse les.—There are but few muscular fibres met with in the region of the ankle: the flexor digitorum brevis arises upon the instep ; and posteriorly we find some of the fibres of the flexor pollicis longus, which are here continued down a considerable way upon the tendon.
c. Arteries.---The arteries about the ankle, from their liability to injury and disease, become of great interest. Upon the instep the course and relations of the anterior tibial artery de mand particular attention ; the vessel here does not run exactly in the median line of the foot, but is somewhat nearer to the inner than to the outer malleolus : we may always reach it with perfect certainty, by cutting between the tendon of the extensor digitorum longus, and that of the extensor pollicis ; these overlap it upon either side, and afford considerable protec tion against wounds or other injuries. Not withstanding the facility of reaching the vessel in this situation, it is by no means advisable to do so when it is at all possible to avoid it, inas much as to expose the artery here it is necessary to wound the synovial sheaths, and inflammation and adhesionwould be the probable consequence of such an injury. The branches of the in ternal malleolar artery are found upon the part of the region, running upon and in front of the inner ankle, and anastomosing with others passing forwards from the posterior tibial, thus insuring a sufficient supply of blood to the joint, even when the trunk of the anterior tibial itself has been tied. But these vessels are of much inferior importance compared with the posterior tibial, whose main trunk lies in the fossa between the heel and the malleolus internus. It is here occasionally the subject of operation, and hence its course and relations should be very carefully noted. We have al ready enumerated the tendons passing beneath the annular ligament in this situation ; the most anterior is that of the tibialis posticus, imme diately behind it lies that of the flexor digi torum, and still more posteriorly, at the interval of about an inch, is found the tendon of the flexor pollicis ; in this interval between the two latter tendons runs the posterior tibial artery, not however equidistant from both, but nearer to that of the flexor digitorum ; it rests upon the tibia and internal tibio-tarsal ligament, and is covered by the integuments and annular ligament ; its venw comites run one upon either side ; and the posterior tibial nerve lies close behind it, but as the vessel descends get ting gradually to its inner side. Notwith
standing the few coverings of the artery in this situation, yet owing to the heel, the ankle, and the tendo Achillis projecting around, and hearing off as it were those coverings from it, the vessel is here at a considerable depth from the surface ; and any one who supposes it can be easily found in the living subject; will form a very erroneous idea of its true position :—hence it is that all good writers on surgical anatomy recommend us to take up the artery in the lower third of the leg, rather than in the calceo-malleolar groove. Several small vessels ramify about the outer ankle, the external malleolar coming from before meets here with the terminating branches of the peroneal artery from behind, but these small vessels are interesting to the sur gical pathologist rather than to the regional anatomist or operative surgeon.
d. Veins.—Two veins, the " venT comites," accompany each of the larger arteries : in all operations upon the artery, the close apposition of the veins, and the possibility of mistaking one for the other, should be remembered by the surgeon. In front of the inner malleolus we observe one or two openings in the fascia, through Which small branches of communication pass between the superficial and deep veins ; these, no doubt, are the principal channels through which the venous blood of the integu ments about the foot and instep is returned, after the operation of tying the great saphena vein.
e. Lymphatics.—The lymphatics consist like wise of two sets ; the one lying beneath the integuments and scattered irregularly over the region ; the other lying beneath the fascia, and for the most part accompanying the blood vessels. Some anatomists speak of a lymphatic gland lying upon the instep, and receiving several of these deep absorbents; in the majo rity of cases there is no such gland, and its existence in any appears to us extremely doubtful.
f. Nerves.—The nerves in this region have the same general distribution as the arteries. In our account of the larger arteries, we have already minutely assigned the relation which their accompanying nerves hear to them. We may thus briefly enumerate them :—in front, the musculo-cutaneous and anterior tibial ; on the inner side the terminal ramifications of the internal saphenus and the posterior tibial ; and on the outside, the terminal branches of the external saphenus. For further particulars re specting the nerves, we refer to the articles LUMBAR NERVES; SACRAL NERVES.