We must follow our mouthful of food, and see how this action takes place.
When the different juices have all done their work, the _chyme_, which is food as it passes from the stomach into the duodenum or passage to the lower stomach or bowels, becomes a milky substance called _chyle_, which moves slowly, pushed by numberless muscles along the bowel, which squeeze much of it into little glands at the back of the bowels.

These are called the mesenteric glands; and, as each one receives its portion of chyle, a wonderful thing happens.

About half of it is changed into small round bodies called corpuscles, and they float with the rest of the milky fluid through delicate pipes which take it to a sort of bag just in front of the spine.

To this bag is fastened another pipe or tube--the thoracic duct--which follows the line of the spine; and up this tube the small bodies travel till they come to the neck and a spot where two veins meet.
A door in one opens, and the transformation is complete.

The small bodies are raw food no more, but blood, traveling fast to where it may be purified, and begin its endless round in the best condition.