THE SYMPATHETIC NERVE. 567 



muscles on either side, their insertion being nearly parallel 

 to the median line, can push it straight forwards or turn it 

 for some distance towards either side. 



Physiology of the Spinal Nerves. 



Little need be added to what has been already said of 

 these nerves (pp. 493 to 495). The anterior roots of the 

 spinal nerves are formed exclusively of motor fibres ; the 

 posterior roots exclusively of sensitive fibres. 



Beyond the ganglia all the spinal nerves appear to be 

 mixed nerves, and to contain as well sympathetic fila- 

 ments. 



Of the functions of the ganglia of the spinal nerves 

 nothing very definite is known. That they are not the 

 reflectors of any of the ascertained reflex actions through 

 the spinal nerves, is shown by the reflex movements 

 ceasing when the posterior roots are divided between the 

 ganglia and the spinal cord. 



PHYSIOLOGY OF THE SYMPATHETIC NERVE. 



The sympathetic nerve, or sympathetic system of nerves, 

 obtained its name from, the opinion that it is the means 

 through which are effected the several sympathies in 



hypoglossal ; 5, pliaryngeal branch ; 6, superior laryngeal nerve ; 7, 

 external laryngeal ; 8, laryngeal plexus ; 9, inferior or recurrent laryn- 

 geal; 10, superior cardiac branch; u, middle cardiac ; 12, plexiform 

 part of the nerve in the thorax; 13, posterior pulmonary plexus ; 14, 

 lingual or gustatory nerve of the inferior maxillary; 15, hypoglossal, 

 passing into the muscles of the tongue, giving its thyro-hyoid branch, 

 and uniting with twigs of the lingual ; 16, glosso -pliaryngeal nerve ; 1 7, 

 spinal accessory nerve, uniting by its inner branch with the pneumo- 

 gastric, and by its outer, passing into the sterno-mastoicl muscle ; 18, 

 second cervicle nerve ; 19, third ; 20, fourth ; 21, origin of the phrenic 

 nerve, 22, 23, fifth, sixth, seventh, and eighth cervical nerves, forming 

 with the first dorsal the brachial plexus ; 24, superior cervical ganglion 

 of the sympathetic ; 25, middle cervical ganglion ; 26, inferior cervical 

 ganglion united with the first dorsal ganglion ; 27, 28, 29, 30, second, 

 third, fourth> and fifth dorsal ganglia, 



