Excerpt from The National Geographic Magazine, Vol. 32: Index, July to December, 1917 The greater size Of the brown rat read ily distinguishes it from either Of the other species. It averages from one to one and a half pounds in weight and about 18 inches in length. Occasional giants of its kind occur, however, as shown by the capture, near Canterbury, England, Of one huge individual weigh ing over four pounds and measuring 2m inches in length. With an abundant food supply brown rats increase with almost incredible rapid ity. They have from three to twelve litters a year, each containing from six to more than twenty young, the average being about ten. The young begin to breed when less than three months Of age. Rats are nocturnal and as a rule keep hidden during the day in holes and other places of concealment about buildings or in burrows which they dig in the ground. Within their retreats they make warm nests Of shredded fibrous material, Often cut from costly fabrics, in which their naked and helpless young are safely brought forth. After careful investigation the United States Public Health Service estimates that the number Of rats living under nor mal conditions in our cities equals the human population, but that in country districts they are relatively three or four times as numerous. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.