PREFACE.

HYGIENE has been defined to be that branch of medicine the end and aim of which are to point out the conditions on which health depends, and the means by which that inestimable blessing may be sustained in all its purity and entirety.

Hygiene embraces, therefore, all those matters which, when in a normal condition, and properly used, contribute to make up, to perfect, and to sustain health; but which, on the contrary, when abused, retained, taken in excess, in insufficient quantity, or in a vitiated or corrupt state, lead to disorder or disease.

of "

This division of the healing art, under the name NON-NATURALS," received at the hands of the ancient physicians, so far, at least, as their limited knowledge would admit, the greatest attention and consideration.

By the term "non-naturals" were understood all those things which are essential to life, but which

neither enter into the composition of the animal œconomy, nor form part of the living body.

These comprehend air, foods and drinks, motion and rest, sleep and wakefulness, secretions, excretions, and retentions, mental emotions, clothing, bathing, &c.

Non-naturals formed, either in part, or as a whole, the subjects of numerous essays and dissertations. Hippocrates has left us a treatise, Περὶ 'Αέρων, Υδάτων, Kai TóжTwν, an example which was followed by Galen, Aëtius, Rhases, Avicenna, Celsus, and others, and, in later times, by Sennertus, Blanchard, &c.

These primitive efforts to attain to a due knowledge and accurate estimate of the beneficence, wisdom, and design in creation, of the adaptation of means to the end, and of those universal, fixed, and immutable laws upon the due observance of which health and life depend, and upon the violation of or departure from which disorder, disease, or death ensues, though worthy of respectful consideration, are frequently obscured by, and inextricably interwoven with, the fanciful speculations, the theoretical opinions, and peculiar dogmas of each period.

The rapid strides, however, which natural philosophy, chemistry, and physiology have made during

the last quarter of a century in the hands of Faraday, Prout, Humboldt, Owen, and other savans, both of this and other countries, have rendered clear, intelligible, and easy of demonstration, much which before existed but as random guesses and as glimmerings in the dark.

This advance of modern science, and the simultaneous march of civilization, having outstripped alike the writings and the theories of the "old fathers" of physic, a manifest deficiency has arisen in the literature of this branch of medicine, which the author ventures to hope he may, in some measure at least, contribute to supply.

On matters of Hygiene we have in this country no standard authority, no single work, no condensed summary, no manual even, to which to refer. Its immutable and life-giving principles are scattered through piles of volumes, rich in all the mysteries and wonders of creation and of science, but on which, be our resources never so ample, we have often the greatest toil and the utmost difficulty to fasten.

At a time when so deep an interest is evinced in "Sanitary Reform" and "Public Health," it may be useful, both to the professional and general

b

reader, to have some work of easy reference to which to turn on the great variety of subjects which these matters involve.

It is to endeavour to supply this desideratum that the writer has ventured to embody all that seems to be necessary to be acquired on those various subjects which make up and constitute Hygiene.

The necessity for a treatise on this subject has become more apparent since the examining boards of both branches of the public service, the army and navy, of the East India Company's medical service, of the University of London, and other licensing bodies, have proclaimed their opinions of the importance of a due knowledge of Hygiene, by making it one of the subjects of examination of the candidate for a commission, or for their degree in, or licence to practise medicine.

The author's aim is to present to his professional brethren, to the medical student, and to the public at large, a plain and faithful transcript of accurate research, observation, and experience, a simple and exact statement of facts and of admitted truths, together with such inferences and deductions as the subject may appear to warrant and demand. With