758 A MANUAL OF ANATOMY 



Their efferent vessels, for the most part, unitC) on either side, to 

 form a lateral aortic lymphatic trunk, right and left, which opens 

 into the receptaculum chyli. Some pass to the pre-aortic glands, 

 and others to the retro-aortic glands. 



Retro-aortic Glands. — ^These glands are about four in number, 

 and they lie behind the abdominal aorta. Their afferent vessels 

 are derived from the pre-aortic and lateral aortic glands, as well as 

 from the vertebral bodies and ligaments to which they are related. 

 Thexv efferent vessels unite to form a single trunk, called the retro- 

 aortic lymphatic trunk, which opens into the receptaculum chyli. 



Diaphragm — Origin — Sternal Portion. — By two fleshy slips from 

 the back of the ensiform process close to its lower end. Costal 

 Portion. — By six fleshy slips, at either side, from the inner sur- 

 faces of the lower six costal cartilages, which interdigitate with 

 slips of the transversalis abdominis. Vertebral Portion. — From the 

 external and internal arcuate ligaments, and the fronts of the 

 bodies of lumbar vertebrae, as well as the intervertebral discs and 

 anterior common ligament, by two crura, the right crus reaching 

 usually as low as the disc between the third and fourth lumbar 

 bodies, and the left as low as the disc between the second and 

 third. 



Insertion. — ^The central tendon on all sides. 



Nerve-supply. — ^The right and left phrenic nerves, each of which 

 springs chiefly from the anterior primary division of the fourth 

 cervical nerve, and usually receives a branch from the third, and 

 sometimes from the fifth. Each phrenic nerve, on approaching the 

 diaphragm, divides into branches which pierce 'its muscular part 

 separately in front of the central tendon, and are distributed on the 

 abdominal surface of the muscle. In the right half of the muscle a 

 communication takes place between the right phrenic nerve and the 

 right inferior phrenic sympathetic plexus, a small ganglion, called 

 the ganglion diaphragmaticum, being situated at the place of com- 

 munication. A similar connection is established on the left side, 

 but no ganglion is present. 



Arterial Supply. — (i) The inferior phrenic branches of the 

 abdominal aorta ; (2) the superior phrenic (comes nervi phrenici) 

 and musculo-phrenic, both branches of the internal mammary 

 of each side ; (3) the phrenic branch of the superior epigastric 

 of the internal mammary of each side ; and (4) branches from the 

 lower intercostal arteries. 



Lymphatics. — ^These pass to the sternal, anterior mediastinal, 

 posterior mediastinal, intercostal, and lumbar glands. 



Action. — ^The diaphragm by its contraction increases the vertical 

 diameter of each half of the thorax, and is therefore a muscle of 

 inspiration. The middle portion of the central tendon is fixed by 

 reason of the fibrous portion of the pericardium, which is implanted 

 into it, being connected above with the deep cervical fascia. The 

 fleshy portion, however, becomes flattened, and descends towards 

 the abdomen, displacing the viscera, and so increasing the vertical 



