About two thirds of the ventral portions of the scalenus muscle should be removed. Do this in two or three steps to make sure the structures medial to the muscle will not be destroyed. Remove about half of the muscle's thickness with a knife to make it more pliable. Then separate the muscle from the underlying structures by hand and finish removal using the scalpel.

Further clean out the nerves of the brachial plexus. As you remove the fatty tissues identify and preserve the phrenic nerve, the vagosympathetic trunk, recurrent laryngeal nerve, the esophagus, trachea, axillary vessels, and caudal deep cervical lymph nodes in this area.

Technique: Preferably exercise blunt dissection using a pair of scissors. Place the closed scissors in connective tissue next to a structure, puncture the connective tissue and spread the scissors. Almost always the fatty tissue and the connective tissue are the weakest parts and will rupture while the important tissues remain intact. Even thin walled veins can be saved this way.

Observe the extent of the left lung. Remove the left lung by pushing the dorsal edge down. This puts tension on the connective tissue linking the lung with the mediastinum (this is the pulmonary ligament). Score the connective tissue with a knife to loosen the caudal part of the lung. Avoid scoring the accessory lobe of the right lung which appears ventral to the esophagus. With a knife cut the bronchi and pulmonary vessels. When finished studying the lung, wrap, label and store it.

Take note that the 6th rib marks the cranial extent of the diaphragmatic projection.

The vagus and phrenic nerves are easily seen coursing in the mediastinum. Score the mediastinum along the nerves and carefully remove the connective and fatty tissue. The tissue located dorsal to the aorta and brachiocephalic trunk contains the thoracic duct. Approach the duct using blunt dissection with scissors or the round tipped forceps, even your fingers.

Removing the tissue located dorsal to the brachiocephalic trunk and aorta requires the utmost care in order to preserve the vascular branches, nerves and thoracic (lymphatic) duct. Popesco Fig. 130 provides a benchmark for this work.