90 



MAMMALIAN ANATOMY 



A TYPICAL LUMBAR VERTEBRA. 



The Fourth Lumbar Vertebra.- -The body is six-sided, with 

 greater cephalo-caudal than transverse diameter ; it is flattened in a 

 dorso-ventral line, so that the height is not more than half the width. 

 The flat dorsal and ventral surfaces are parallel, as are the smaller 

 lateral surfaces. The cephalic and caudal surfaces are similar. They 

 are almost rectangular, with the transverse width twice as great as the 

 dorso-ventral height (Fig. 59). 



FIG. 59. 



Neural Spine. 

 Cephalic Articular Process 



Mammillary Process 



Neural Lamina. 

 Accessory Process 



Transverse Process. 



A LUMBAR VERTEBRA, ANTERIOR OR CEPHALIC ASPECT. 



The transverse processes are thin plates which have their origin 

 on the cephalic half of the edge between the ventral and lateral 

 surfaces, and are directed ventrally, laterally, and toward the head. 

 They present cephalic, caudal, and lateral edges, and dorsal and 

 ventral surfaces. Their cephalic and caudal edges are almost parallel. 

 They are slightly sinuate, but the cephalic edge is more or less emar- 

 ginate, the caudal more or less arcuate. The end is cut off obliquely, 

 so that the lateral margin is directed from the caudal end medially 

 and toward the head, forming a sharp acute angle with the cephalic 

 edge and an obtuse, sometimes indefinite, angle with the caudal edge. 

 The dorsal and ventral surfaces are, in the main, flat, with their 

 cephalo-caudal diameter equal to half the transverse diameter. 



The ventral surface (Fig. 60) is faintly convex in a cephalo-caudal 

 direction, and is sometimes ridged for muscular attachment. It faces 

 ventrally and toward the middle line. 



