It is recommended that all dissection groups remove the left leg and specific groups will be asked to remove the both legs. It is important to understand that the removal of the thoracic limb involves breaking down the synsarcosis that attaches the thoracic limb to the trunk (ie extrinsic muscles of the thoracic limb).
Remove the support hook from the scapula. Stand in front of the horse and reach between the front legs to place the edge of the knife into the fold between the thorax and the medial side of the leg (axillary area). Cut through the skin and the pectoral muscle group. Apply lateral tension to the distal portion of the limb to separate the scapula and associate tissues from the trunk. Cut through the vessels and nerves of the brachial plexus leaving as much of these structures on the limb as possible (NOTE: This will make nerve identification on the limb much easier). Next transect the latissimus dorsi muscle, serratus ventralis thoracis and cervicis muscles, and the brachiocephalicus muscle. The leg is now only attached by the dorsal portion of the synsarcosis; the thoracic trapezius muscles and the rhomboideus muscle. Cut these from below the scapula and the leg will be separated. Wrap up the leg, label it and store it on the rack inside the cooler.
To gain access to the thoracic cavity ribs 1, 3-5, and 7-9 need to be removed in the ruminant and in the horse the following additional ribs 10-13. Make an incision caudal to the 2nd rib and caudal to the 5th rib. Make an incision caudal to the 6th rib and caudal to the 13th rib. Extend all incisions dorsally to meet with the ventral border of the iliocostalis muscle and ventrally to the attachments of the costal cartilages. Use the large shears to free the ribs at both their dorsal and ventral extremities. Now remove the 1st rib. Carefully cut the ventral part of the scalenus muscle at the attachment to the first rib prior to cutting out this rib.