206 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



a living animal, and measures t h< - outflow per unit of time. An increase iu 

 the outflow means a dilatation of the vessels, diminution means constriction. 

 He finds thai the outflow diminishes in the rabbit when the vagus is stimulated 

 in the neck, and increases when the cervical sympathetic is stimulated. Franck 

 measures the pressure simultaneously in the pulmonary artery and left auricle, 

 a method apparently also trustworthy. The stimulation of the inner surface 

 of the aorta causes a rise of pressure in the pulmonary artery and a simul- 

 taneous fall in the left auricle, indicating, according to Franck, the vaso-con- 

 strictor power of the sympathetic nerve over the pulmonary vessels. A reflex 

 constriction is also produced by the stimulation of the central end of a branch 

 of the sciatic, intercostal, abdominal pneumogastric, and abdominal sympa- 

 thetic nerves (see Fig. 45). 



Heart. — Vaso-motor fibres lor the coronary arteries of the heart have been 

 described. 1 



Intestines.' 2 — The mesenteric vessels receive vaso-constrictor fibres from the 

 sympathetic chiefly through the splanchnic nerve. The vaso-constrictors of 

 the jejunum, as a rule, begin to be found in the rami of the fifth dorsal nerves ; 

 a little lower down, those for the ileum come off; and still lower down, those 

 for the colon ; none arise below the second lumbar pair. According to Hal- 

 lion and Franck, vaso-dilator fibres are present in the same sympathetic nerves 

 that contain vaso-constrictors. The dilator fibres are most abundant or most 

 powerful in the rami of the last three dorsal and first two lumbar nerves. 

 There is some evidence of the presence of vaso-dilator fibres in the vagus. 

 The excitation of the vaso-constrictor centres by the blood in asphyxia pro- 

 duces constriction of the abdominal vessels. The vaso-dilator as well as the 

 vaso-constrictor fibres of the splanchnic probably end in the solar and renal 

 plexuses. 



Liver. — Cavazzani and Manca 3 have recently attempted to show the pres- 

 ence of vaso-motor fibres in the liver. Their method consists in passing warm 

 normal saline solution from a Mariotte's flask at a pressure of 8 to 10 milli- 

 meters Hg through the hepatic branches of the portal vein and measuring 

 the outflow in a unit of time from the ascending vena cava. On stimulating 

 the splanchnic nerve they observed that the outflow was usually diminished 

 though sometimes increased, indicating perhaps that the splanchnics contain 

 both vaso-constrictor and vaso-dilator fibres for the hepatic branches of the 

 portal vein. The vagus appeared to contain vaso-dilator fibres. Further 

 studies are necessary, however, before pronouncing definitely upon these 

 questions. 



'Porter: Boston Medical and Surgical Journal, 1896, ex xxiv. 39 ; Porter and Beyer: Ameri- 



Journal of Physiol xj ij, 1900, iii. j>. xxiv. ; Maass : Archiv fiir du : ,< ammte Physialogie, 1899, 

 Ixxiv. p. 281. 



- rlallion ami Franck : Archives de Physiologie, 1896, xxviii. pp. 478, 193 ; Bunch : Journal <>f 

 Physiology, 1899, xxiv. p. 72. 



'< avazzani and Manca: Archives italiennes <l>' Biologic, L895, xxiv. p. :;:;; Franpois-Franck 

 and Hallion: Archives d Physiologie, L896, pp. 908, 923; 1897, pp. 134, 148. 



