EXTERNAL SECRETIONS 493 



Destructive diseases of the liver e.g., acute yellow atrophy, suppuration, 

 cirrhosis largely diminish the production of urea, but increase the quanti- 

 ties of the ammonium salts in the urine. The same is true when the liver 

 cells are destroyed during acute phosphorus poisoning. 



The Conjugation of Products of Protein Putrefaction. One of the 

 important functions of the liver is the conversion of toxic compounds, the 

 products of the putrefaction of proteins, into non-toxic compounds. These 

 compounds are formed in the intestine, are absorbed and carried by the blood 

 of the portal vein to the liver. In their passage through the capillaries of 

 the liver they are conjugated for the most part with potassium sulphate by 

 the action of the liver cells and thus deprived of their toxicity. Among the 

 substances thus conjugated are indol, skatol, phenol, and cresol. After 

 absorption indol and skatol are oxidized to indoxyl and skatoxyl and then 

 combined with potassium sulphate giving rise to potassium indoxyl sul- 

 phate and potassium skatoxyl sulphate. Phenol and cresol are apparently 

 directly combined with potassium sulphate. All of these compounds then 

 pass into the blood of the general circulation and finally are eliminated by 

 the kidneys. Potassium indoxyl sulphate or indican is the source of the 

 indigo-forming substance found in the urine. Other compounds are like- 

 wise reduced in toxicity by the liver cells though the methods by which this 

 is accomplished vary with the nature of the compound. The liver thus 

 presents a chemic defense against the entrance of more or less toxic agents 

 into the blood of the general circulation. 



