Page:Defensive Ferments of the Animal Organism (3rd edition).djvu/41

 with the milk as sole nourishment, from the moment of passing on to the mixed nourishment that is peculiar to its species, the second important change in the feeding of the growing individual is accomplished. The third stage of its evolution has begun.

The cells must function quickly to prevent disharmonious substances from entering the circulation. To ensure the proper discharge of a duty so important to the organism, the liver is placed between the intestines and other organs. Within this important organ the blood, still laden with the absorbed and partly metamorphosed food-stuffs, comes into contact with the liver cells. This material is once more thoroughly sifted, and the blood is finally discharged into the general circulation, freed from all substances that would be out of harmony with the body and the blood.

The knowledge that digestion is the means by which unsuitable products are prevented from passing into the blood and the cells of the body is of the greatest importance for our comprehension of the whole metabolism of the animal organism. Thus, to a certain extent, we may look upon the animal organism as a whole in itself. All the cells of the