48 HUMAN PHYSIOLOGY 



reality a kind of waste product, only a product which 

 is made useful in the economy of the body. 



THE LIVER AND PEPTONES. The first duty of 

 the liver is to deal with the peptones or changed 

 nitrogenous foods which we have seen to be 

 conveyed to it from the stomach. The liver cells 

 deal with these peptones and exert a certain 

 chemical action upon them, the effect of which is to 

 change them into a suitable form for being added to 

 the blood. A somewhat curious point in the history 

 of peptones refuses to be noted. If peptones them- 

 selves were allowed to pass into the blood 

 unchanged from the liver, they would give rise to 

 symptoms of body-poisoning, and there seems little 

 reason to doubt that many cases of so-called bilious 

 disorder are really due to interference with the 

 liver's work in this respect. That our food, other- 

 wise of perfectly healthy character, may therefore 

 injuriously affect us if proper chemical changes are 

 not effected upon it is obviously a remarkable fact 

 of our constitution. The liver in this respect might 

 be compared somewhat to a filter which stands 

 between the food on the one hand and the blood on 

 the other. It is a fact of some interest in relation 

 to the liver's work that actual poisons taken into the 

 body may be detected in the liver more readily 

 perhaps than in any other organ of the body, the 

 liver exercising here, the same filtering action such 

 as it discharges naturally in the process of digestion. 



THE LIVER AND SUGAR. The second duty of the 

 liver is that of dealing with the sugar-foods which 

 represent either sugar taken as such, or starches 

 which we have seen are converted into sugar by 

 digestive action. From the intestine sugar is ab- 

 sorbed and carried to the liver by the portal vein. In 



