Stowei.l. N^i'7-ves in tlic Domestic Cat. 291 



the dorsal muscles or integument, making it possible to use 

 the dextral side to corroborate and to correct results obtained 

 by dissecting the sinistral. The exposure of the myel in the 

 arch of the caudal thoracic vertebra (thirteenth) exposes the 

 ectal origin of the first lumbar nerve. The arch can be re- 

 moved in a similar manner caudad and dextrad as the dissec- 

 tion requires, using the precaution to trace the dorsal division 

 of each nerve before removal of the dorsal muscle. The 

 nerves should be traced from the ectal origin peripherad. 



LUMBAR NERVES. NERVI LUMBALES. 



Co}n?non Characters. — The lumbar nerves are seven pairs, 

 and have characters in common. They are related with the 

 sympathic system by anastomotic filaments to the adjacent 

 ganglia (Fig. PI. S. and S.), w^hich filaments leave the ental 

 surface of the nerve as it traverses the groove from the neural 

 arch to the inter-vertebral foramen (foramen of exit); these 

 anastomotic filaments are apposed to an arteriole — the dorsal 

 branch of the A. lumbalis. At the ectal border of the fora- 

 men of exit, each nerve divides into a dorsal and ventral 

 portion; the dorsal nerve divides into two or more branches, 

 which innerve the muscles of the back (MM. quadratus lum- 

 borum, erector spinas, intervertebrales) (Fig. M. dor,), which 

 are especially large in the cat. A branch from each dorsal 

 nerve can be traced to the integument (Fig. Int.), where it 

 joins in an open plexus with the adjacent nerves. 



The nerve trunk or ventral division dips ventrad close to 

 the border of the centrum and mesad of the diapophysis; the 

 origin is thus concealed by fascia, aponeuroses and super- 

 posed muscles. At the ventral border of the centrum the 

 nerve usually passes laterad (except the branch to form the 

 lumbar plexus) apposed to the abdominal branch of the lum- 

 bar artery. From the ental surface of the trunk adjacent to 

 the centrum a branch is given oft' which separates into three 

 to five ramuli to the proximal or aponeurotic portions of the 

 M. psoas (Fig. Pso.), and two anastomotic rami to the sym- 



