■292
��ivoi- v., mo. iu.
��as to which the Iiiiliaiia ciueUre thai the iaiaiiil W8B oDce the eeinetcij Tor the neighboring mainlnud, nnil therefore will not allow llie tnoiinds to be explored.
Subsequently, near the village of Sail Migiiel, Mr. Miller examined and photogni[>hed the ruins of an old church, sur- rounded by a pavement of smooth, Hal stones, carefully laid in cement, but uow cov-
��ered with ciirlh. Tlic iiihaliitants suy that this pavement extendi: for half a mile around the cluirch, and that a broad, |)avc(I way once led from the church to the water, a mile awav.
��KRRORSIN DIGESTION EXPERIMENTS.
Hknneiiekij and Stohmnnn, in their Bei- triige zur rationellen /Htlerung der wiederkduer, published in ISliO, reported practically the first determinations of the digestibility of the proxi- mate constituents of cattle-foods. Since tbat time, H large number of similar determinatione upou various fodders, and with the several species of domestic auimals, have been made, chiefly, if not entirely, by the German experi- ment-stations. In these deterini nations the method employed by Hennebcrg and Stoh- manu, and which is here given in outline, lias been universally followed.
The food of the animal is weighed, suitable account being taken of any portion left un- eaten, and a sample of the food is subjected to chemical analysis. The solid excrement of the animal, which consists for the most part of the undigested [rortions of the food, is also carcfullv colkctoi, neighed, -iiid aunlyzed.
��B'rom these data, it is a i^imple matter to com- pute how much dry matter or how niiioli of any jmrticular ingredient of the food the ani- mal received, and what part of lliis failed to be digested. This method of experiment evidently will give directly the digMti- bility of any fodder wbicli can be made the exclusivi' food of the animal. In lite case of material like grain, meal, ami the con- centrated fodders in gen- eral, the matter is uotijuite so simple. In this ease it '\s iirst necessar^v to deter- mine the digestibility of a sample of hay, or other («arsc finder. This done, the animal is given a mixture of this coarse fotlder and the concentrated foiider in question, and the ' ~ amount of this mixture which is digested is de- termined. Then, on the assumption that the same proportion of
- ^3 the coarse fodder
— - was digestM in
the second trial as in the first, we ciilciilate how much of the con- centrated fodder must have been digested iu order to yield the results observed u[H>n the
Certain sources of error have been ignored in the general statement given above. Thus the excretion is always more or less irregular from liar to day ; and the excreted matter con- tains, iu addition to undigested fooil. moi'e or less intestinal mucus, and renmauls ofdigestire Juices, which, though small in amount rela- tively, are not entirely to be neglectc<l. Then it has recently been shown that some )iortion9 of the food fail to appear in the excreta, because they suffer a fermentation in llie ali- mentary canal, rather than because they arc digested in any proper sense. This is particu- larly the case with cellulose (see Science. No. 1 00, p. i 1 ) . Finally, the methods of analj-sis in use for fodder and excrement are not ill all respects capable of ginng sharjily deflned results.
Another class of errors, the small unavoid- able errors of weighing and chemical analysis, usually loss considered, may grow to verv t siderable dimcnsiouK when inuUipticd m
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