96 [NERVES OF LIVER AND KIDNEY. 



not dependent on integrity of the vagus nerves. Its 

 activity is associated with increased circulation of blood 

 in the mucous membrane, and with changes in the secret- 

 ing cells, comparable with those already described in 

 other glands. Nothing can, however, as yet be stated 

 with certainty as to the relation of these changes with 

 the process. 



TJie liver. The secretion of bile cannot be directly 

 excited by any mode of acting on the nervous system. 

 Excitation of the spinal cord, which at first increases the 

 discharge of bile, by producing constriction of the bile- 

 ducts, eventually diminishes it. The secretion of bile is 

 arrested by even very slight increase of pressure in the 

 bile ducts ; whenever this happens bilin and colouring 

 matter exist in the circulating blood (jaundice). The 

 power of the liver cells to store glycogen is annulled by 

 destruction either of the centre which controls its blood- 

 vessels or of the channels by which that control is exer- 

 cised ; in either case the urine becomes saccharine (glyco- 

 suria). A similar effect is produced by curare, carbonic 

 oxide and some other poisons, as well as by central exci- 

 tation of the vagus. 



The kidneys possess no secreting nerves: the renal 

 nerves have no other function excepting that of constric- 

 tors of the arteries. The rate of secretion of urine is 

 directly influenced by the state of the circulation : thus, 

 it can be increased in animals by augmentation, and 

 diminished by reduction, of the pressure under which 

 blood enters the glomeruli. It can be diminished or even 

 arrested by increasing the pressure in the renal veins. 

 By destruction of the renal vascular centre in the floor of 

 the fourth ventricle, or of the renal nerves, the vascular 

 tone of the kidneys is annulled, in consequence of which 

 the urine flows abundantly (polyuria) and often contains 

 albumin (albuminuria), but is not necessarily saccharine. 

 Similar effects are observed after severance of the renal 



