Vertebral Column 33 



forwards and outwards and are nearer together than the wider upper pair, which are 

 curved to look inwards and backwards to receive them. Mammillary tubercles are 

 present on the back aspect of the upper processes, to afford origin to post- vertebral 

 muscles. Lamina deep but short, and the spine is horizontally directed, thick and 

 square-cut, when viewed from the side. 



The lumbar column rests on the top of the sacrum, with which it makes a prominent 

 lumbo-sacral angle, owing to the sudden change in direction as the sacrum turns back- 

 wards and downwards : the sharpness of the angle, however, is modified by the 

 construction of the last lumbar body to form a transitional bone. Thus it occurs that 

 this body is wedge-shaped, markedly deeper in front, and its spine is much smaller 

 owing to the limitation of space resulting from the backward turn of the sacrum : this 

 last character is more marked in the female, owing to the more pronounced sacral 

 bend. The spinal foramen is triangular and large, containing the nerves that constitute 

 the cauda equina with their coverings. 



FIFTH LUMBAR VERTEBRA. In addition to the modifications already noticed 

 in the body and spine, the transverse processes are not very long, but are thick and 

 strong, arising not only from the arch, but spreading their bases forward on to the 

 body : it thus happens that the issuing nerve must pass over this base, so that the 

 upper intervertebral notch is described as grooving it. * From this broad base the 

 process narrows to a blunt tip, to which the ilio-lumbar ligament is attached. This 

 strong band, helping to support the column between the two innominate bones, 

 accounts for the strength of the process, and also for its direction, which is upwards 

 as well as outwards. The lower articular processes articulate with the sacral processes, 

 which are far apart, so that on the last lumbar vertebra the lower processes are practi- 

 cally as far apart as the upper. The upper and lower processes together form a mass 

 which projects somewhat into the neural canal, sharpening its outer angles, and in 

 front of this the pedicles show inner margins thinner than in the higher bones, below 

 which a sloping surface leads to the lower intervertebral notch. 



Examination of the upper and lower borders of the lumbar bodies enables one to 

 recognise the position of certain attached structures (Figs. 27 and 35). 



Each border, along the lateral aspect of the body, is rendered heavy and thick 

 by the connection with it of a fibrous sheet that is thrown across the concavity of the 

 body and affords origin to the Psoas : the sheet and the muscle may encroach on the 

 bone to a greater extent than in the figure, as may be seen on some bones by observing 

 the extent and depth of the roughened area. 



The concave surface between these ridges lodges the lumbar vessels and twigs 

 from the sympathetic. 



The anterior common ligament covers the front of the body between these lateral 

 areas, and the ridges to which it is fixed are less prominent than at the sides ; it 

 separates the aorta and origins of the lumbar arteries from the bone. The crura of 

 the diaphragm are attached to this ligament and through it to the upper two or three 

 lumbar bodies, but no distinct marking can be assigned to them on the bones. 



The Psoas also obtains origin from the front of all the lumbar transverse processes. 

 The extent of this origin appears to be somewhat variable, but, being by muscular 

 fibre, it leaves no mark on the bone ; there is, however, a tendinous slip generally in 

 the lower and inner part of each of these origins, and a corresponding slight roughening 

 is to be found at the inner end of the lower border of the process. 



* The transverse process of the fourth exhibits a tendency to forward extension like the fifth. 

 F.A. 3 



