PHYSIOLOGY OF THE LIVER AND SPLEEN. 751 



the experiments made by, this author together with later experiments 

 reported by others,* 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. Motor fibers may occur also in the vagi. Sensory 

 fibers capable of causing a reflex constriction or dilatation of the 

 bladder are found in both the vagus and splanchnic nerves. Stim- 

 ulation of the central end of the cut splanchnic 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 intestine. 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. When the 

 flow of bile is prevented by ligation of the bile-duct, or when this 

 duct is occluded by pathological changes the bile eventually gets 

 into the blood, producing. a condition of jaundice (icterus). There 

 has been much discussion as to whether the bile is absorbed directly 

 into the blood from the liver cells or the liver lymph-spaces, or 

 whether it is carried to the blood by way of the lymph-vessels and 

 thoracic duct.f Experimental evidence points to both possibili- 

 ties. The increased pressure in the bile system leads possibly to a 

 rupture of the delicate bile capillaries, and the bile thus escapes 

 into the lymph-spaces. From these spaces it may be absorbed 

 directly by the blood-vessels of the liver, or it may be carried off 

 in the lymph-stream toward the thoracic duct. 



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 proteins 

 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 



* Bainbridge and Dale, "Journal of Physiology," 1905, xxxiii., 138. 

 t See Mendel and Underbill for literature, "American Journal of Phys- 

 iology," 1905, xiv., 252. 



