When the preliminary draft of the Ninth Decennial Revision of the U. S. Pharmacopoeia appeared two years ago, indicating important and radical changes in the proposed text, the author at once began conforming this work to that standard - rewriting many subjects and bringing all within current scientific thought. That labor, conceded from the first somewhat prodigious, has drawn its "slow length along," sustained by inherent duty and sentiment, until its completion - a form considered greatly in advance of its predecessors. Advantage has also been taken of the Fourth Edition of the National Formulary to the extent of embracing most of its drugs and preparations in abstract, with doses whenever necessary - a logical inclusion believed imperative in order to afford the student a positive familiarity with both of our legal authorities.

The arrangement of the drugs remains strictly the same as that followed in previous editions, being based upon the principle of associating as nearly together as possible those substances, organic and inorganic, which have a common or allied origin, allowing those next related to follow in regular order, the basal or parental source thus being kept paramount. Vegetable drugs, therefore, appear in the order of natural historic relationship of the plants from which obtained - i. e., botanic sequence, beginning with the more simple and gradually approaching those more complex. That this might be possible and in accord with Nature's process of evolution, the classification of Engler and Prantl, as enunciated in their Die Naturlichen Pflanzenfamilien, has been followed, modified, however, occasionally in accordance with Engler's Syllabus der Pflanzenfamilien, and also Britton and Brown's Illustrated Flora. Animal drugs also are treated so as to be in harmony with this great natural law of development of the animals from which obtained - i. e., zoologic sequence, beginning with the lower and proceeding always to those of higher organization. Organic drugs, carbon and synthetic compounds are arranged similarly, their chemical relationship, however, being borne always in mind.

Measurements are expressed in the metric system, followed by approximate equivalents in the English, and temperature is stated in both Centigrade and Fahrenheit scales, thereby giving an equal opportunity for use according to individual preference. Doses are stated in the apothecaries' and metric system, in the hope that the easy comparison of parallel quantities may produce a stronger mental impression, and thereby become an element toward metric education. The abbreviation Ml. (millilitre) has been given preference, that of Cc. (cubic centimetre) following parenthetically.

The accent of generic and specific names continues to be placed on the final letter, consonant or vowel, of the accented syllable (not simply upon the vowel of that syllable) - certainly the most rational method, and one by which it is believed the student will obtain more readily an intelligent idea of pronunciation. Several pages will be found devoted to the pronunciation of words more or less troublesome to the average student, the aim having been to follow the best philologists rather than general usage.

The treatise on the microscope has been retained, not so much in the belief that it represents a sufficiently exhaustive exposition of the subject, as the hope that the primitive essentials there outlined may suggest to pharmacists and physicians, at least, the importance of the domain and the ultimate need in it of even more advanced and technical knowledge.

A number of new illustrations, elucidating plant characteristics, have been introduced in the hope of aiding visual instruction.

The work, in its entirety, approaching nearer a new than a revised one, has had to have, from the mechanical side, a resetting and recasting, the older plates being discarded in toto, certainly most conducive to the fullest liberty at remodeling for improvement - a privilege that has unstintingly been exercised.

The author wishes to renew his sense of gratitude to those who in their teaching have used the work, thereby aiding its dissemination, and to those who have contributed suggestions as well as encouragement, thereby leading to its betterment. Especially is he indebted to the publishers for an increasing interest and willingness to perform, in accordance with highest art, their portion of the labor.

David M. R. Culbreth, M.D. Baltimore, 1917.