102 HUMAN PHYSIOLOGY 



bile elements (bile acids) absorbed from the intestine are 

 especially active. 



The pressure in the bile ducts may be higher than that in 

 the portal vein, yet the secretion of bile is dependent upon 

 blood pressure. If the blood pressure decrease, less bile is 

 secreted and the bile contains more solids. Ligaturing the 

 portal vein, stimulation of the spinal cord and of the 

 splanchnic nerve (because of diminished amount of blood 

 carried to the liver, due to the constriction of the arteries), 

 cause inhibition of bile secretion. 



Secretory nerves for the liver have not yet been demon- 

 strated. 



5 . The discharge of bile. 



The bile is driven out of the liver by the pressure of the newly 

 made bile. The ductus choledochus has at its opening into the 

 intestine a sphincter which regulates the flow of the bile. The 

 muscles of the gall-bladder and ductus choledochus also aid in 

 discharging the bile. The nerves for these muscles are supposed 

 to be the vagus and splanchnic. 



If the flow of bile is prevented, the bile enters the lymph vessels 

 and thence passes into the blood (jaundice). The bile is then 

 excreted by the kidneys. 



6. SECRETION OF INTESTINAL JUICK 



To investigate the secretion of the intestinal glands, an intes- 

 tinal fistula must be made. A piece of the intestine is isolated 

 but. its connection with the mesentery is not severed. Either both 

 ends of this piece of intestine are sewn into the incision of the 

 abdominal wall, or only one end is thus fixed while the other is 

 closed by a ligature. The two ends of the main intestine are sewn 

 together. 



1. Composition of intestinal juice. The juice of the small 

 intestine is a colorless, alkaline fluid having a specific gravity 

 of 1.007. It contains besides salts, some proteids, a diastatic 

 and an inverting ferment, and, according to some authors, a 

 proteolytic ferment. 



The large intestine furnishes a mucous secretion without 

 ferments. 



2. The secretion. The intestinal juice is the secretion of 



