730 PHYSIOLOGY OF DIGESTION AND SECRETION. 



the experiments made by this author together with later experiments 

 reported by Freese, that the bladder receives both motor and in- 

 hibitory fibers by way of the splanchnic nerves. These fibers emerge 

 from the spinal cord in the roots of the sixth thoracic to the first 

 lumbar spinal nerve, and pass to the celiac plexus by way of the 

 splanchnic nerves. Sensory fibers capable of causing a reflex con- 

 striction or dilatation of the bladder are found in both the vagus and 

 splanchnic nerves. Stimulation of the central end of the cut splanch- 

 nic causes a dilatation of the bladder (reflex stimulation of the 

 inhibitory fibers), while stimulation of the central end of the vagus 

 causes a contraction of the bladder and a dilatation (inhibition) of 

 the sphincter muscle at the opening of the common duct into the in- 

 testine. Since these last movements are the ones that occur during 

 normal digestion, it is probable that the afferent fibers from the 

 duodenum, which are concerned in this reflex, run in the vagus. 



Effect of Complete Occlusion of the Bile-duct. It is an in- 

 teresting fact that, when the flow of bile is completely prevented by 

 ligation of the bile-duct, the stagnant liquid is not reabsorbed by the 

 blood directly, but by the lymphatics of the liver. The bile pig- 

 ments and bile acids in such cases may be detected in the lymph as it 

 flows from the thoracic duct. In this way they get into the blood, 

 producing a jaundiced condition. The way in which the bile gets 

 from the bile-ducts into the hepatic lymphatics is not definitely 

 known, but possibly it is due to a rupture, caused by the increased 

 pressure, at some point in the course of the delicate bile capillaries. 



General Physiological Importance of Bile. The physiological 

 value of bile has been referred to in speaking of its several constitu- 

 ents. Bile is of importance as an excretion in that it removes from 

 the body waste products of metabolism, such as cholesterin, lecithin, 

 and bile pigments. With reference to the pigments, there is evidence 

 to show that a part at least may be reabsorbed while passing through 

 the intestine, and be used again in some way in the body. The bile 

 acids represent end-products of metabolism involving the proteids 

 of the liver cells, but they are undoubtedly reabsorbed in part, and 

 can not be regarded merely as excreta. As a digestive secretion, the 

 most important function attributed to the bile is the part it takes in 

 the digestion and absorption of fats. It accelerates greatly the action 

 of the lipase of pancreatic juice in splitting the fats to fatty acids and 

 glycerin, and it aids materially in the absorption of the products 

 of this hydrolysis. A number of observers have shown that when a 

 permanent biliary fistula is made, and the bile is thus prevented from 

 reaching the intestinal canal, a large proportion of the fat of the food 

 escapes absorption and is found in the feces. This action of the 

 bile may be referred directly to the fact that the bile acids serve as a 

 solvent for the fats and fatty acids. It was formerly believed that 



