348 PHYSIOLOGY CHAP. 



that division of this nerve produced a marked fall of lateral 

 pressure in the aorta, while stimulation of the peripheral end 

 of the divided nerve raised the pressure above that which 

 obtained before section. On investigating the state of the 

 visceral vessels after section, marked congestion was observed 

 in the venous portal system, with distinct hyperaemia of the 

 small vessels of the mesentery, intestinal canal, and renal 

 parenchyma. These effects are more pronounced in the rabbit 

 than in the dog (Asp), apparently because in herbivores the 

 gastric canal is much longer than in carnivores. 



The constrictor fibres of the splanchnic run to the coeliac 

 plexus, and thence to the stomach, intestines, and kidneys. 

 Excitation of the splanchnic on one side only causes the vessels 

 of both kidneys to contract (Cohnheim and Eoy). 



The constrictor fibres of the hepatic vessels also emerge from 

 the splanchnic, and pass to the coeliac plexus, and thence to the 

 liver, along the bile-duct and hepatic artery (Vulpian). The 

 vaso-constrictors of the spleen come from the left splanchnic, 

 and perhaps also from the right (Roy). 



It is known from other observations that the great splanchnic 

 does not contain all the vaso-constrictor fibres of the abdominal 

 viscera. The lesser splanchnic has fibres of the same character 

 (Asp), and the abdominal branches of the vagus also appear to 

 contain vaso-constrictors for the spleen (Oehl). 



Next to the great splanchnic, the vaso-constrictor nerve 

 which supplies the most extended tract is certainly the cervical 

 sympathetic, which not only regulates tonicity in the vessels of 

 the ear, as discovered by Claude Bernard, but also exerts its 

 constrictor function on all other external and internal vessels of 

 the head, as appears from the investigations of several observers. 



It was plain from the work of Budge and Waller (1853) that 

 the constrictor fibres of the cervical sympathetic did not arise in 

 the ganglia situated along its course, but in the anterior roots of 

 the spinal nerves, whence they emerged by the rarni communi- 

 cantes. The constrictor fibres run principally with the vessels 

 round which they form a plexus ; but they are partly associated 

 with the cerebral nerves, leaving them again later, to join the 

 vessels. Thus the hypoglossal and lingual branches of the 

 trigeminal contain vaso-constrictor fibres for the tongue (Vulpian). 

 The facial nerve, again, contains many fibres of the same kind, so 

 that division of this nerve is followed by a rise of temperature in 

 the whole face (Cl. Bernard). These vaso-constrictor fibres do 

 not originate in the centres of the cerebral nerves, seeing that 

 destruction of these centres produces no sign of vascular paralysis. 

 They probably emerge from the sympathetic. 



It is, however, possible that besides the constrictor fibres from 

 the sympathetic, the vessels of the head are affected by other 



