J2 THE VERTEBRAL COLUMN. 



the superior, concave, look backwards and inwards; the inferior, convex, look forwards 

 and outwards. The superior pair are farther apart than the inferior, and embrace 

 the inferior pair of the vertebra above them. From each superior articular process 

 a tubercle projects backwards, which corresponds to the superior tubercle of the 

 dorsal transverse process, and is called the mamillary process (metapophysis). 



The foramen is large and triangular, or widely lozenge-shaped. 



The fifth lumbar vertebra is massive, the body is much deeper in front than 

 behind, the transverse processes are broad and conical, the lower articular processes 

 are wider apart than the upper, and the lamina project into the spinal foramen on 

 each side. 



While in the European the bodies of the lumbar vertebrae are collectively deeper in front 

 than behind, in conformity with the curvature of this - part of the column, the individual 



Fig. 11. FIFTH LUMBAR VERTEBRA, FROM ABOVE. (Drawn by D. Gunn.) 



segments show some difference in this respect. Thus, the first lumbar vertebra is deeper 

 behind than in front ; in the second the anterior and posterior vertical diameters are nearly 

 equal ; and the third, fourth and fifth are characterized by a preponderance of the anterior 

 depth, which increases progressively from above downwards. In the dark races of man 

 (Australian, Bushman, Andamanese, Negro) the depth of the five lumbar bodies together is 

 greater behind than in. front, and the fifth is the only one in which the anterior depth notably 

 exceeds the posterior. It does not appear probable, however, that this conformation of the 

 vertebral bodies is accompanied by a less marked degree of lumbar curvature, since the latter 

 is determined mainly by the intervertebral discs. (W. Turner. Journ. Anat., xx, and 

 " Challenger " Reports, Zoology, xvi ; D. J. Cunningham, ' ; The Lumbar Curve in Man and 

 Apes," Dublin, 1886, and Proc. Roy. Soc., 1889.) 



Varieties in number of the moveable vertebrae. The number of the cervical vertebrae 

 is remarkably constant. The dorsal and lumbar vertebrae may vary reciprocally, the total 

 remaining the same, according to the number of ribs present. Thus, if there are only eleven 

 pairs of thoracic ribs, the twelfth vertebra will have lumbar characters ; while in the more 

 frequent case of a thirteenth pair of ribs being developed, the corresponding vertebra might 

 ba regarded as dorsal, although, in general conformation, it usually more resembles the 

 lumbar type. The whole number of true vertebras may be diminished or increased by one. 

 In the former state the first sacral vertebra will be the 24th, as is the case generally in the 

 orang, and, if the number of the ribs remain normal, there will be only four lumbar vertebras. 

 In the case of increase, the first vertebra to articulate with the hip-bone will be the 26th, and 





