684 CHARLES W. HOOPER 







Pawlow (1893) with Eck fistula dogs, also show that the liver protects 



the body from the poisonous action of the ammonia compounds formed in 

 the normal digestive hydrolysis of proteins hy converting them into urea. 



Most of the protein nitrogen in the daily diet of an adult is excreted 

 within twenty-four hours as urea. Levene and Kober (1909) found that 

 when single amino-acids were fed to dogs they were excreted entirely as 

 urea. The experiments of Van Slyke and Meyer (1913) point to the liver 

 as the organ which is most active in absorbing amino-acids from the blood 

 stream during normal digestion, and in submitting them to the chemical 

 alterations which precede elimination as urea, or storage as reserve pro- 

 tein. ' Amino-acids injected into the circulation are absorbed by all tis- 

 sues: those taken up by the liver disappear rapidly. The ammo nitro- 

 gen content of this organ may be doubled by an injection of amino-acids 

 into the general circulation, and yet return to normal within two or three 

 hours. During the period required by the liver to rid itself entirely of 

 absorbed amino-acids, no appreciable diminution has occurred in that 

 stored in the muscles. From other organs they disappear less rapidly than 

 from the liver. The disappearance of the amino-acids from the liver is 

 accompanied by an increase in the urea of the blood. Van Slyke, Cullen 

 and McLean (1915) operated on dogs at varying intervals after feeding, 

 and found the urea content of the blood from the hepatic vein 3 to 20 per 

 cent higher than that of the portal blood. A similar increase in the urea 

 content during passage of the blood through the muscle tissue did not 

 occur. Van Slyke (1916) presents sound experimental proof that the 

 blood in passing through the liver takes from it about as much nitrogen in 

 the form of urea, as it gives to it in the form of amino-acids. 



It is generally agreed, therefore, that the liver deaminizes the greater 

 part of the amino-acids and is the organ most concerned in the synthesis of 

 urea. However, urea formation is not a process entirely confined to the 

 liver. Kaufmann (1894), Nencki and Pawlow (1897) and Fiske and 

 Summer (1914) have proved that dogs may still form urea to some extent 

 when the liver is excluded from the circulation. 



Evidence of Internal Secretion from Administration 

 of Hepatic Substance and Derivatives 



Liver Substance. Eapid emaciation, malnutrition and anemia of 

 dogs with biliary fistula?, and the eagerness of the animals to lick the 

 bile from the fistula 1 , all suggest the need of this body fluid. The ex- 

 periments of Hooper and Whipple (a) ( 1916) indicate that bile is essential 

 for the life of an animal on a mixed diet of meat, bones and bread. If 

 bile is wholly excluded from the intestinal tract, the dog loses ground 

 steadily, shows intestinal disorders, accompanied by blood in the fcces, 



