is necessary. Valuable and trustworthy information upon hygienic topics such as can be followed with confidence to beneficent results has been but slowly acquired, and is yet far from perfect; but enough has been accumulated to work a sanitary revolution in society if reduced to general application. Of course, in matters of personal hygiene everything depends upon individual knowledge, and the disposition to use it; but the efficiency of measures for the promotion of public health is hardly less dependent upon popular intelligence. Needful sanitary laws may be passed, but the essential thing, after all, is that they shall be faithfully and vigorously carried out and not remain dead letters in the statute-book. This must depend upon the degree to which the people are instructed in hygienic subjects and are alive to the care of health. Hygiene has grown in recent years into an important branch of study, with a copious literature of monographs and manuals. Cyclopædias have been attempted, but they have hitherto been hastily compiled and are altogether inadequate for their purposes. We can, however, no longer complain of the want of a comprehensive and authoritative treatise upon this many-sided subject. The work before us covers the full ground, is thoroughly digested, and constitutes of itself a tolerably complete hygienic library.
This elaborate work seems to have had the following origin: In reproducing Ziemssen's "Cyclopædia of Practical Medicine" from the German, the editors and publishers found that the first volume, relating to the subject of public health, had been prepared so entirely from the German standpoint, and took cognizance of a state of things so materially different from that which exists in this country, that it was considered advisable to omit it in the American edition. But as the subject was of fundamental importance, it was felt that this omission must be repaired, by taking up the subject with special reference to the different climates, conditions of soil, habitations, modes of life, and laws of the United States. In this way the deficiency of Ziemssen's "Cyclopædia" would be amply repaired, so that its subscribers might possess the work in its completeness, while the hygienic volumes would be of interest to physicians generally, and also to the educated classes, who are acquiring a growing interest in the subject.
The introduction by Dr. John S. Billings, besides prefatory explanations, treats of the causes of disease and the jurisprudence of hygiene. After considering the various definitions of hygiene, and showing how its meaning may be so extended as to sweep in immense tracts of human knowledge. Dr. Billings says: "The hygiene of which this volume is to treat has not so broad a scope as that just hinted at, since the intention has been to produce a practical treatise limited to a consideration of the most usual preventable causes of disease in civilized countries, and more especially in the United States, and of the surest and most economical means of diminishing or destroying these causes."
The following remarks are still further illustrative of the ideas involved in the scheme of this work: "To what extent the prevention of disease, the prolongation of life, and the improvement of the physical and mental powers in man may be carried, we do not know; but no doubt the tendency of those who write and speak most on this subject is to exaggerate the possibilities of improvement; since it does not seem probable that the conditions of perfect personal and public health are attainable, except in rare and isolated cases, and for comparatively short periods of time; yet 'that the average length of human life may be very much extended, and its physical power greatly augmented; that in every year within this Commonwealth thousands of lives are lost which might have been saved; that tens of thousands of cases of sickness occur which might have been prevented; that a vast amount of unnecessarily impaired health and physical debility exists among those not confined by sickness; that these preventable evils require an enormous expenditure and loss of money, and impose upon the people unnumbered and immeasurable calamities, pecuniary, social, physical, mental, and moral, which might be avoided; and that means exist within our reach for their mitigation or removal; and that measures for prevention will effect more than remedies for the cure of disease'—will probably be admitted by every one who has carefully studied the subject and made him-
