55. The spines of the vertebræ may be useful as landmarks indicative of the levels of important organs. I have therefore arranged them in a tabular form, thus:-- TABULAR PLAN OF PARTS OPPOSITE THE SPINES OF THE VERTEBRÆ. { 5th. Cricoid cartilage. Œsophagus begins. CERVICAL. { 7th. Apex of lung: higher in the female than in the { male. (30) { 1st. { 2nd. { 3rd. Aorta reaches spine. Apex of lower lobe of lung. { Angle of bifurcation of trachea. (49) { 4th. Aortic arch ends. Upper level of heart. { 5th. { 6th. DORSAL. { 7th. { 8th. Lower level of heart. Central tendon of diaphragm. { 9th. Œsophagus and vena cava through diaphragm. Upper edge of spleen. { 10th. Lower edge of lung. Liver comes to surface posteriorly. Cardiac orifice of stomach. { 11th. Lower border of spleen. Renal capsule. { 12th. Lowest part of pleura. Aorta through diaphragm. Pylorus. { 1st. Renal arteries. Pelvis of kidney. (83) { 2nd. Termination of spinal cord. Pancreas. Duodenum just below. Receptaculum chyli. LUMBAR. { 3rd. Umbilicus. Lower border of kidney. { 4th. Division of aorta. (65) Highest part of ilium. { 5th. 56. =Origins of the spinal nerves.=--It is useful to know opposite what vertebræ the spinal nerves in the different regions arise from the spinal cord. They arise as follows:-- The origins of the eight cervical nerves correspond to the interval between the occiput and the sixth cervical spine. The origins of the first six dorsal nerves correspond to the interval between the sixth cervical and the fourth dorsal spines. The origins of the six lower dorsal nerves correspond to the interval between the fourth and the eleventh dorsal spines. The origins of the five lumbar nerves correspond to the interval between the eleventh and twelfth dorsal spines. The origins of the five sacral nerves correspond to the spines of the last dorsal and the first lumbar vertebræ. 57. =Movements of the spine.=--The movements of which the spine is capable are threefold: 1. Flexion and extension; 2. Lateral inclination; 3. Torsion. Flexion and extension are freest between the third and the sixth cervical vertebræ, between the eleventh dorsal and the second lumbar, and between the last lumbar and the sacrum. This is well marked in severe cases of opisthotonos, where the body is supported on the back of the head and heels.[4] Still better may it be observed when a mountebank bends backwards, and touches the ground with his head. The lateral movement is freest in the neck and the loins.