Page:Popular Science Monthly Volume 19.djvu/139

Rh attached by archæologists. They were kept at the Smithsonian Institution for two months, and were carefully examined there by members of the National Academy of Sciences as well as by other persons; heliotype plates were taken of them, and they were exhibited at the meeting of the American Association at Boston last August. Mr. Pratt believes that the evidence of their genuineness is sufficient. The society's collection of mound-relics is regarded as one of the best in the world.

The Saliva and the Gastric Juice.—Recent researches reported by M. Defresne throw new light on the relations of ptyaline, diastase, and the gastric juice. It has been debated whether the saliva is destroyed in the gastric juice or continues in the stomach its action on starch. M. Defresne's experiments prove that the saliva is paralyzed in pure gastric juice, but that with a mixed gastric juice containing only organic acids, saccharification proceeds as well as in the mouth. Ptyaline, then, differs from diastase in that it is only paralyzed for an instant in pure gastric juice, but recovers its action in the mixed gastric juice and in the duodenum, and is capable of continuing the process of saccharification; while diastase is irrecoverably destroyed in hydrochloric solutions or in pure gastric juice, and is profoundly altered after passing into the mixed gastric juice, so that if it still dissolves starch it no longer saccharifies it. Ptyaline is recommended as an excellent reagent for demonstrating the difference between mixed gastric juice, which owes its acidity to organic acids, and pure gastric juice, the strength of which is derived from hydrochloric acid.

Cutting and Slave-making Ants.—The Rev. Henry C. McCook has contributed to the Academy of Natural Sciences, of Philadelphia, papers on a Northern cutting ant, and on the American slave-making ant, both of which are of much interest. The cutting ant was observed at Island Heights on Tom's River, New Jersey. Entrance to the nest was afforded by a narrow tubular gallery about two inches long, which led to a spherical chamber about an inch and a half in diameter. This chamber, or vestibule, communicated with another chamber, also generally spherical, but of more irregular outline, three and a half inches in diameter, within which were several masses of leaf-paper similar to that made by the Texas leaf-cutting ant, but exceedingly fragile and without the cellular arrangement of the Texas paper. In pleasant weather the insects worked in two columns, one going each way—to the pine-trees and returning to the nest—and moving very deliberately. Those in the column returning homeward were carrying little pieces of the pine-needle or leaf, cut from seedling plants. They bore the load on the head, with one end held firmly by the mandibles, and the effect at a little distance was "to give them a shoulder-arms appearance." In cutting the leaf, the ant climbed out to a position near the end and applied her mandibles, moving around as she cut, till the piece was severed and fell. The architecture of the caves was a miniature copy of those of the Texas cutting ant. All the colonies were comparatively small, and without visible connection with each other. The slave-making ants (Polyergus lucidus) were studied near Altoona, Pennsylvania. They occupied a chambered nest which was furnished with four gates, and extended to the depth of at least twenty-two inches underground; but the chambers were without orderly arrangement, apparently on account of the gravelly nature of the soil in which they were built. Mingled in large numbers with the lucidus ants were working insects, of the species Formica Schauffussi. Two days after the nest was disturbed, the working ants were observed cleaning out the galleries, with the apparent intention of closing the openings. Others were engaged in a migration, taking up the mistress ants by interlocking mandibles with them, and carrying them off up the perpendicular face of the cutting for eighteen or twenty inches, and then for the distance of six feet over the ground and through the grass. "More than once a slight opposition was made to this treatment. The slaves, or at least certain individuals of them, . . . seemed at times to have a prejudice against the presence of lucidus ants above-ground, and would unceremoniously seize them and carry them