THE POPULAR SCIENCE MONTHLY
and the Sierra Nevada on the west. The present volume does not include all the results of Professor Cope's researches, for another is to follow. Professor Hayden well says of the whole, in his letter transmitting the report, that "the amount of new matter toward the origin and history of the mammalian groups brought together by the author in these two volumes is most extraordinary, and will probably never be surpassed." In this single volume are given the vertebrata of the Eocene and of the Lower Miocene, less the Ungulata, with descriptions of 349 species, which are referred to 125 genera. The author sums up fifteen important results that have accrued through the researches here set forth in the discovery of new genera and families, among which are the discovery of the phylogenetic series of the Canidæ, or dogs, and the same of the ancestors of the Felidæ, or cats. As the book was stereotyped in 1883, all conclusions of later date than that are necessarily excluded from it; but the author's final conclusions from the material described are mostly to be found in a series of illustrated articles he has been publishing in the "American Naturalist" in the years 1883-'85.
The Ten Laws of Health; or, How Diseases are produced and prevented. By J. R. Black, M. D. Published by the Author. Baltimore. Price (by subscription), $2.50.
A part of this book was published several years ago. The edition having been exhausted for many years, the matter has been revised to bring it up even with the progress of the age, and an entirely new part has been added, comprising nearly a fourth of the present volume, on thorough disinfection within the sick-room and the sick-bed as the most effective means for preventing the spread of contagious diseases and epidemics. The author is a strong believer in the doctrine that disease is unnecessary and preventable; in his view man is the most sickly of beings, because those—which means most men—"who neither know nor strive to be governed by law in the uses they make of themselves, become victims to hundreds of evils in the various forms of disease." The ten laws of health are taken up in their order and explained; the violations of them are shown, with their attendant results; and the mode of observing them is taught. The first law is, that a pure air must be breathed. To obtain this within the house, supposing that the surroundings arc pure, "the great and imperative requirement is air-movement, a decided though gentle current through an occupied room day and night." Second; the food and drink must be adequate and wholesome. The evil to be guarded against in the United States is excess, for inadequateness or a deficiency of food on this continent, although the common sentiment is quite the reverse, is not often a direct cause of disease. As to the quality of our food, as we prepare it, "of the many books published on the subject of cooking, there are few, if any, that have not receipts by the score which can not be excelled for producing indigestion." The effects of tea and coffee and alcoholic stimulants are carefully considered. The third law enforces the necessity and judicious practice of out door exercise; and the fourth law prescribes adequate and unconstraining covering for the body. The fifth law concerns the exercise of the sexual function. Under the head of the sixth law are considered the effects of changes of climate, and the measures to be taken for safe acclimatization when that step is taken. Regarding changes of climate for the sake of health, the author concludes, from a survey of the available facts on the subject, "that an imprudent change of climate more frequently destroys the health of the healthy than it cures the sickness of the sickly." The seventh law relates to the choice of occupation. Its admonition is to select such pursuits as do not cramp and overstrain any part of the body, or subject it to irritating and poisonous substances; and, of course, to avoid those of an opposite character. Next, we are to keep personally clean, bathing systematically and changing regularly all clothing next to the skin. "Those who for month after month, and even for year after year, do not cleanse and invigorate the skin by frequent baths, followed by brisk friction of the skin, lose the good offices of a very active organ of regeneration, and cause their blood to be in a state very favorable for the production of disease from slight causes." Ninthly, we must preserve the mind in a tran-