THE SPINAL NERVES. 159 



the nerve which conveys to the brain the sense of pain, 

 which accompanies complaints of the chest and abdomen. 

 It is joined by another nerve called the spinal accessory ; 

 which not being a true cranial nerve we have put in a 

 paragraph by itself. 



The spinal accessory nerves (Plate V. Fig 1 . 8, 8) derive 

 their origin from filaments given off by the fourth and fifth 

 spinal nerves. As they enter the skull, they join the eighth ; 

 when emerging thence each divides into two branches ; 

 one of which pierces the sterno maxillaris, and can be 

 traced within the interior of the muscle as low as the 

 sternum : the other slants off across the neck, and can be 

 ibllowed as low down as the trapezius muscle. 



The ninth, or lingual pair {Plate V. Fig 1.9), take their 

 origin from the corpus pyramidale ; and both pass along the 

 branch of the posterior jaw to gain the root of the tongue ; 

 and seem thus to be peculiarly appropriate to its locomo- 

 tion, as the gustatory are to the function of taste. 



The tenth pair, or suboccipitals (Plate V. Fig 1 . 10, 10), 

 are a pair of the spinal nerves. They arise from the com- 

 mencement of the spinal marrow ; and are distributed to the 

 muscles of the head and neck. 



THE SPINAL NERVES. 



The spinal marrow gives off the spinal nerves in pairs : 

 the names and number of each spinal nerve corresponding 

 with the vertebrse themselves. Hence there are seven cer- 

 vical, eighteen dorsal, six lumbar, and Jive sacral nerves. 

 Each spinal nerve owns a double origin by filamentary 

 bundles ; one coming from the upper, and the other proceed- 

 ing from the under, division of the spinal cord. The fila- 

 ments of the upper origin are sentient ; that is, they convey 

 sensation only to the brain ; and the filaments of the lower 

 origin are entirely motor ; that is, they carry from the brain 

 to the muscles the influence which enables them to contract 

 upon the mere wish of the individual. The two filaments, 

 each originate separately ; and each being gifted with such 

 opposite powers, are upon the point of leaving the spinal 

 canal when they encounter a ganglion. The superior fila- 

 ments, as might be supposed, pass over this ganglion ; and 



