Anatomy, physiology and hygiene . s coiled upon itself and extendsfrom the pylorus to the large intestine, which begins inthe right lower portion of the abdomen. Its opening intothe large intestine is guarded by the ileo-coecal valve, anarrangement which readily admits of the passage of refusematerial into that intestine, but interposes a usually ser-viceable barrier to its return. The intestine is held in place principally by the mes-entery, a double fold of serous membrane1 attached tothe spinal column; but it so envelops the intestine thatits necessary peristalticmovements in the trans-miss
Anatomy, physiology and hygiene . s coiled upon itself and extendsfrom the pylorus to the large intestine, which begins inthe right lower portion of the abdomen. Its opening intothe large intestine is guarded by the ileo-coecal valve, anarrangement which readily admits of the passage of refusematerial into that intestine, but interposes a usually ser-viceable barrier to its return. The intestine is held in place principally by the mes-entery, a double fold of serous membrane1 attached tothe spinal column; but it so envelops the intestine thatits necessary peristalticmovements in the trans-mission of food are notinterfered with. The lining of the in-testine is very vascularand velvety. Through-out the larger part ofthe canal it is arrangedin transverse, shelf-likefolds,-more or less circu-lar in form, which, fromtheir winking motionas they sway backwardand forward in thefluids of the intestine,are called valvulae con-niventes. There areabout eight hundred of these delicate foldsthe passage of food, and so expose i( for. Fig. 52. Section of Small Intestine, showing Valvulae Con-niventes (Testttt). Wide perpendicular line =muscle ; line on left = fibrous coat ; line on right= mucous membrane. They retarda lonerer time 1 A membrane which secretes a thin whey-like thud called serum. Asimilar membrane, under the name o( the peritoneum^ incloses, for themost part, all the abdominal viscera, in the same way. 120 DIGESTION. to the action of the digestive fluids. They also providea very large surface for secretion and absorption. The characteristic velvety condition of the mucousmembrane is due to its millions of minute elevations, pre-senting a general appearance of plush, and known asintestinal villi. Through them the process of absorption is
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