I056 A MANUAL OF ANATOMY 



distribution to the first and seond intercostal spaces shown. The vessel will 

 be found descending in front of the neck of the first rib. A branch from the 

 first aortic intercostal artery — that, namely, to the third space — should be 

 looked for ascending over the neck of the third rib to join the second inter- 

 costal artery, which it sometimes replaces. 



The thoracic portion of the gangliated cord of the sympathetic should now 

 be dissected. It will be found lying over the heads of the ribs under cover of 

 the parietal pleura, and gradually inclining inferiorly on to the side of the 

 vertebral column. Two rami communicantes are to be shown passing between 

 each ganglion and the adjacent intercostal nerve, and it is to be noted that 

 these rami are very short. The vascular branches of distribution of the upper 

 ganglia, as well as the branches to the posterior pulmonary plexus of nerves, 

 are not easy of dissection, but the splanchnic nerves admit of this readily, 

 the great and small splanchnic nerves being constant, but the least being 

 frequently absent. 



The upper surface of the diaphragm is next to be dissected, and attention 

 should be directed to (i) its thoracic relations, (2) the central tendon, (3) the 

 foramen quadratum, (4) the aortic and oesophageal openings, and (5) the 

 relation of the sympathetic cords and splanchnic nerves to it. The diaphragm 

 may now be laid open, in association with the dissectors of the abdomen, 

 and the thoracic duct is then to be followed down to its commencement in 

 the receptaculum chyli. Thereafter the subcostal muscles should be dis- 

 sected. They will be found over the back parts of the ribs in the vicinity 

 of the angles. 



Articulations. — i. Vertebral Column. — The part available for the dissec- 

 tion of the ligaments is the portion below the first thoracic vertebra, and 

 probably as low as the tenth or eleventh thoracic vertebra. The ligaments 

 to be dissected are (i) the anterior common ligament, which is easily dis- 

 played ; (2) the posterior common ligament, to show which th? neural arches 

 of the vertebrae must be removed by sawing through the pedicles ; (3) the 

 intervertebral discs, which are to be dissected by means of transverse and 

 vertical sections ; (4) the ligamenta subflava, which connect the laminae, and 

 are readily seen after removal of the neural arches ; (5) the capsular liga- 

 ments, which connect the articular processes ; (6) the supraspinous and inter- 

 spinous ligaments ; and (7) the intertransverse ligaments. 



The movements of the vertebral column are to be carefully studied. 



2. Ribs — Costo-central Joints. — The ligaments to be dissected are (i) the 

 anterior costo-central or stellate, easily recognised ; and (2) the inter- 

 articular, which is only seen on opening the joint, and which is absent in 

 the first, sometimes the tenth, the eleventh, and twelfth joints. The two 

 synovial cavities are to be noted, except in the case of the joints just enume- 

 rated as having no interarticular ligament. 



Costo-transverse Joints. — The ligaments to be dissected are the posterior, 

 middle, and superior costo-transverse. Within the posterior costo-trans- 

 verse ligament the synovial membrane of the joint is to be shown. The 

 middle costo-transverse or interosseous ligament can only be studied properly 

 by sawing horizontally through the neck of the rib and the adjacent trans- 

 verse process. The superior costo-transverse ligaments are to be displayed 

 as two distinct bands — anterior or external, which is large ; and posterior 

 or internal, which is small. The continuity of the outer border of the anterior 

 ligament with the posterior intercostal aponeurosis is to be shown. 



Costo-chondral Joints. — Each rib is connected to its cartilage by the con- 

 tinuity which takes place between the periosteum of the rib and the peri- 

 chondrium of the cartilage. 



Sterno-chondral Joints. — The ligaments to be dissected are anterior, pos- 

 terior, superior, and inferior. In the case of the second joint, and it may 

 be in some of the succeeding joints, there is an interarticular ligament, which 

 divides the joint into two distinct synovial compartments. The direct con- 

 nection of the first costal cartilage with the manubrium sterni is to receive 

 attention. 



Interchondral Joints. — These are met with from about the fifth to the 



