THE DIGESTIVE SECRETIONS 945 



discoloration of the sclera, conjunctiva and mucous surfaces. This 

 pigmentous material also appears in the urine and finally gives rise 

 to a reduction in the frequency of the heart and respiration and a 

 general bodily and mental fatigue. 



A condition of this kind may arise in consequence of a catarrhal inflammation 

 of the larger biliary passages and the formation of mucous plugs, or in consequence 

 of the escape of a calculus from the gall-bladder which later on becomes firmly 

 wedged in between this organ and the duodenum. Under these circumstances 

 the feces assume a grayish color and the consistency of clay, owing to the absence 

 of bile and the resultant accumulation of much undigested fat. Defecation be- 

 comes infrequent and labored, owing to the loss of the tonicity of the intestinal 

 musculature and the solidity of the fecal material. Jaundice may also be 

 incited by the administration of poisons which, however, do not produce an actual 

 obstruction of the larger biliary passages. The cause of this non-obstructive type 

 of icterus is more difficult to explain, unless it is held that the poison gives rise to 

 an erosion and obliteration of the intralobular channels. This result is quite com- 

 mon in all conditions producing an excessive destruction of red cells. It is generally 

 believed that this resorption of bile takes place through the lymphatics and not 

 through the blood-capillaries, \ because the ligation of the common duct does not 

 give rise to jaundice if the thoracic duct is obstructed at the same time. 



Extirpation of the Liver. — It has previously been shown that the 

 secretion of bile is dependent upon filtration, diffusion and osmosis, 

 and a vital activity of the cells. Attention has also been called to the 

 fact that bile is secreted continuously but not at a uniform rate, be- 

 cause different stimulations result from time to time which vary its 

 formation. Chief among these is the chyme which, upon its ejection 

 into the duodenum, evokes a local reflex and liberates the hormone 

 secretin. By this means the increased activity of the hepatic cells is 

 made to coincide precisely with the evacuation of the gall-bladder, so 

 that both processes occur at about the third hour of digestion and 

 synchronously with the outpouring of the pancreatic juice. In this 

 connection it is of interest to note that the digestive products of the 

 proteins and fats evoke a much more copious flow of bile than the 

 carbohydrates. It may also be increased by a large intake of water, 

 and diminished by hunger and emotions. 



The Ugation of the portal vein does not stop this secretion alto- 

 gether, because the hepatic artery is able for a time to compensate 

 for the loss of the portal blood. But this compensation soon proves 

 wholly inadequate to sustain life and the animal succimibs to a vas- 

 cular depression brought about by the engorgement of the portal 

 circuit. 2 Much better results may be obtained if an artificial com- 

 munication is first established between the portal vein and the inferior 



1 Mendel and Underhill, Am. Jour, of Physiol., xiv, 1905, 252, and Eppinger, 

 Ziegler's Beitr., xxxi, 1903, 230. 



2 The ligation of the portal vein distally to the orifice of the pancreatic vein 

 does not prove fatal, because the blood of the mesenteric veins then flows into the 

 splenic vein, whence it reaches the gastric veins and the hilum of the liver by way 

 of the pancreatic veins. This reversal of the splenic blood stream is made possible 

 by the enlargement of the small veins upon the pylorus, ordinarily connecting the 

 pancreatic vein with the gastric veins. 



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