CONSTITUTION OF THORACIC CORD. 369 



ganglion (splanchnic ganglion) is formed on it, usually confined to the inner part of 

 the nerve, over the last dorsal vertebra, or the last but one ; and when it presents a 

 plexiform arrangement, several small ganglia have been observed on its divisions. 

 According to Cunningham, the splanchnic ganglion is always present on the right 

 side. 



From the great splanchnic nerve and the splanchnic ganglion filaments are given 

 to the front of the vertebrae and the aorta. 



In eight instances out of a large number of bodies, Wrisberg observed a fourth splanchnic 

 nerve (ne.mis s/jf(irirhH/r><* .s-///;/r ///<.*). It is described as formed by offsets from the cardiac 

 nerves, and from the lower cervical as well as some of the upper thoracic ganglia. 



The small splanchnic nerve springs from the ninth and tenth (sometimes the 

 tenth and eleventh) thoracic ganglia, or from the neighbouring part of the cord. It 

 passes along with the preceding nerve, or separately, through the diaphragm, and 

 ends in the lower part of the semilunar (or aortico-renal) ganglion. In the chest, 

 this nerve often communicates with the great splanchnic nerve ; and in some 

 instances it furnishes a branch to the renal plexus, especially if the lowest splanclinic 

 nerve is very small or wanting. 



The smallest splanchnic nerve (nervus renalis posterior, Walter) arises from 

 the last thoracic ganglion, and communicates sometimes with the nerve last 

 described. After passing the diaphragm with the cord of the sympathetic, it ends 

 in the renal plexus. Its place is frequently supplied by a branch of the small 

 splanchnic nerve. 



CONSTITUTION OP THE THORACIC PART OP THE SYMPATHETIC. 



The thoracic portion of the gangliated cord receives most of the spinal fibres entering the 

 sympathetic system (/;/'. p. 359). Only a small part of these end in the thoracic ganglia ; the 

 greater number pass either upwards into the neck or downwards into the abdomen. The fibres 

 ascending to the neck arise from the upper dorsal nerves ; they include the pupillo-dilator 

 fibres, secretory fibres of the submaxillary gland, vaso-motor fibres of the head and neck, 

 accelerator fibres of the heart, and others, all of which have been referred to in connection 

 with the cervical sympathetic (p. 366). In addition to these, the following groups have been 

 demonstrated experimentally in the lower animals : 



() Vaso-constrictor fibres of the pulmonary vessels have been shown by Bradford and 

 Dean, in the dog, to pass out of the spinal cord by the thoracic nerves from the second to the 

 seventh (mainly, however, through the third, fourth, and fifth nerves), and to end in the 

 ganglion stellatum. 



(b~) Vaso-constrictor fibres of the limbs are connected with the vertebral ganglia. 

 Those of the fore limb are given off by the dorsal nerves, in the dog from the third to the 

 eleventh (Bayliss and Bradford), in the cat from the fourth to the ninth (Langley). Those 

 of the hind limb are furnished, according to the same investigators, in the dog by the last 

 three (11, 12, 13) dorsal and first three lumbar nerves, and in the cat by the last two or three 

 dorsal and the first three or four lumbar nerves. 



(r) Secretory fibres to the sweat-glands of the fore foot leave the dorsal nerves from 

 the third or fourth to the ninth, and pass to the ganglion stellatum ; while those of the hind 

 limb emerge by the last two dorsal and upper three lumbar nerves, and descend in the cord 

 to the lower lumbar and upper sacral ganglia in the cat (Langley). 



(d) Pilo-motor fibres in the cat pass from the lower nine or ten dorsal nerves, as well as 

 the upper three or four lumbar, to the vertebral ganglia (Langley). 



The splanchnic nerves contain : 



(e) Viscero-inhibitory fibres of the stomach and intestine. According to Langley 

 and Dickinson they end in the ganglia of the solar plexus. 



(/) Vaso-motor nerves of the abdominal blood-vessels. The existence of vaso-con- 

 strictor fibres for the arteries of the alimentary canal in the splanchnic nerves is well 

 established ; and, according to Langley and Dickinson, these nerves also contain the vaso- 

 dilator fibres of the same vessels : both sets of fibres end in the ganglia of the solar plexus. 

 Vaso-constrictor fibres of the portal vein and its tributaries were originally demonstrated by 

 Mall ; according to Bayliss and Starling, in the dog, they are given off by the dorsal nerves 

 from the third to the eleventh, but mainly from the fifth to the ninth. The nerves of the 

 renal blood-vessels, both constrictor and dilator, are derived in the dog from the dorsal nerves 

 from the sixth downwards, as well as (constrictors only) from the upper two lumbar nerves 



