450 A TEXTBOOK OF PHYSIOLCH : Y 



taken from the plasma protein the particular amino-acids of which it 

 has need. Another part of the urea might also be endogenous in 

 origin, being formed in the liver from the amino-acids resulting from 

 the katabolism of protein in various parts of the body. 



The question as to whether urea is formed solely in the liver should 

 probably, despite views to the contrary, be answered in the negative. 

 There is apparently a small formation of urea from endogenous pre- 

 cursors in other parts of the body, particularly the muscles. Per- 

 fusion of the hind-limbs of an animal with defibrinated blood leads 

 to an increase of the urea content in the venous over the arterial 

 blood. It is correct, however, to say that the main mass of urea 

 execreted from the body is formed in the liver from the nitrogenous 

 moiety of the protein food taken in. 



6. Protective Function. Another important function of the 1 ver 

 is its protective function. This is manifested in various way> : 



( 1 ) The nocuous products of protein putrefaction in the large in- 

 testine, such as indol, skatol, phenol, cresol, are combined in the liver 

 with sulphuric acid to form the innocuous potassium salt of the acid. 



NH :C 8 H 6 + = NH :C 8 H 5 OH 



Indol Indoxl 



NH :CHOH + S0 = NH :C 8 H S .O.S0 3 K + H 2 O 



2 Q 8S .. 3 2 



Potassium Potassium indoxyl 

 a?id sulphate Sulphuric acid (indican) 



CHOH + S0 = C 6H 5 .O.S0 3 K + H 2 O 



Phenol Potassium phenol 



Sulphuric acid 



In cases of excessive formation these bodies are combined v/ith 

 glycuronic acid also. 



(2) Drugs, such as chloral, camphor, etc., are combined with 

 glycuronic acid in the liver, and rendered harmless or less harmful. 



(3) When acid formation is going on within the body for example, 

 the formation of aceto-acetic acid and d-oxy-butjTic acid during 

 starvation, or in pathological conditions such as diabetes mellitus 

 the liver to a certain extent negatives the ill effects of such acids by 

 combining them with ammonia, thereby markedly increasing the 

 ammonia content of the urine. 



(4) The liver possesses the property of retaining' within its cells 

 poisonous minerals, such as phosphorus, arsenic, mercury, antimony. 

 But little is known as to the exact manner in which this is accomplished. 



7. Fibrinogen Formation, The liver is possibly the organ in which 

 the fibrinogen of the blood arises, also antithrombin when peptone 

 is injected into the blood; this, according to the generally accepted 

 view of blood-coagulation, renders the blood and lymph incoagulable 

 the result of such an injection. 



