STOMACH STONES.

New Zealand Mail, Issue 1832, 17 April 1907, Page 23

STOMACH STONES.

It is well known that many birds swallow small stones to assist digestion. This appears to have been the habit also of the extinct j reptiles, the dinosaurs. Associated with their skeletons are often found rounded pebbles which apparently had served them in this way. These “gastroliths;” as they ana called, have, been closely studied by several American observers, who profess to be able to tell them anywhere. Many of these pebbles have arisen in a marine formation which contained silicious nodules, -and probably their original source will be located before long. The dinosaurs of the Big Horn and Colorado localities either picked them up on the ancient shore-line, or found them in - the streams of the district carried down from higher situations. They are said to be unmistakable objects. Merely water-worn stone® have a surface like ground glass, and even when slightly polished ibis smoothness does not extend into any depressions that may be present. Jnfibtt case ■of tlie gastrolith, the original inequality of outline of the pebble may indeed remain; but from being so long in the stomach of the dinosaurs it is worn to a polish much finer than wind and water can produce; so that the result compares with the finest work of the buffing wheel. Quite a quantity of learning has already collected round these stones. The dinosaurs, for example, had a partiality for brightlycoloured pebbles. These discoveries show that the habit of stone-swallow-ing existed anterior to the evolution of birds, who are now its original exponents; but it''seems that several mammals of a low grade of intelligent also swallow such indigestible morsels. Thus the fur-seal, whose shore habits are perhaps not unlike those of th© dinosaurs, chooses bits of lava to regale itself upon. Now and again we come across human individuals who exhibit an unaccountable tendency to swallow strange things. Is this a case of reversion? Although we have;plenty of dinosaur skeletons, we can naturally know little .about their physiology. These gastroliths, however, seem to suggest that they had stomachs comparable to those of birds in the present day. We do know that they wem well provided with gastric Voice, as they also browsed heavily on an out-of-date grass whose tissues contained large amounts of silica; and their stomachs must have been muscular for in some cases they have polished the hardest quartz perfectly smooth.