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The membrane is thrown into many transverse, or circular, folds which increase its surface and also prevent materials from passing too rapidly through the intestine. One important respect in which the small intestine differs from all other portions of the food canal is that its surface is covered with great numbers of minute elevations known as the villi.
The liver requires for the proper performance of its functions plenty of pure blood, hence the necessity for fresh air and exercise, that the lungs may work well. The liver is easily influenced by alcoholic beverages, and by getting too hard work to do through eating rich foods. Two villi containing lacteals. Magnified 100 diameters.
At B are shown little projections of the intestinal wall, called villi extending into this food and covered by a membrane. Inside of these villi are blood-vessels, C, and it will be thus seen that the membrane, B, separates two liquids, one containing the dissolved food outside the villus, and the other containing blood inside the villus.
It has little of the buoyancy which the theme demands, but there is a great deal of sound writing in the concerted music, and some of the ballads are tuneful enough in a rather commonplace way. His best-known work is 'The Night Dancers, an opera founded upon the legend which has been used by the Italian composer Puccini in his 'Le Villi.
As the ovum sinks into this especially prepared bed, the villi are formed. They break open the adjacent capillaries of the mother, thus diverting her blood from its accustomed course. The blood collects in microscopic lakes in contact with the capsule of the ovum, and from them flows back into the mother's veins.
Again, in those animals the ventricles of whose hearts are smooth on their inner surface, without villi or valves, and the walls of which are thin, as in fishes, serpents, birds, and very many genera of animals, the arteries differ little or nothing in the thickness of their coats from the veins.
The blood which thus circulates through the villi, it is important to emphasize, is the child's blood; it cannot escape through the coating of the villi, just as our blood cannot escape through the skin of the fingers. Similarly, the mother's blood cannot enter the child; the two circulations are absolutely separate and distinct.
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