Page:Popular Science Monthly Volume 20.djvu/871

Rh first, time affects consciousness; and it is finally reflected back to the corpus striatum, whence it goes down the motor fibers to perform whatever actions have been decided upon for it by the conscious cells.

no one suppose that m this "short text-book" we have to deal with a primer.

Everything is comparative, and the term "short" here has relation to the enormous development and extent of recent organic chemistry. This solid and comprehensive volume is intended to represent the present condition of the science in its main facts and leading principles, as demanded by the systematic chemical student.

We have here, probably, the best extant text-book of organic chemistry. Not only is it full and comprehensive and remarkably clear and methodical, but it is up to the very latest moment, and it has been, moreover, prepared in a way to secure the greatest excellences in such a treatise. The original "Text-Book of Organic Chemistry," by Adolph Strecker, was a work of great merit, which stood high in Germany, and passed through several editions. The author was vigilant in keeping it up to the time, and was about to enter upon the preparation of the sixth edition, making important changes required by chemical progress, when his labors were cut short by death in 1871. Professor Wislicenus, the accomplished chemist of Würzburg, was then induced after considerable reluctance, owing to the pressure of his official duties, to undertake the task which the author was prevented from accomplishing. This was done in so thorough a manner that, while much of Stacker's best work remained, it received a new cast and a more perfect adaptation, both to the state of the science and to the requirements of those for whom it was primarily intended. So largely was the treatise impressed by the originality of Professor Wislicenus that it became generally recognized as his work; and, when it was proposed to reproduce the book in English, Professor Wislicenus only consented on the condition that the very latest results of research in organic chemistry should be embodied in it. He stipulated that "regard shall be had to the largely increased material and essentially nearer insight into the relations and nature of organic compounds already known, that have been obtained since the publication of the book." Drs. Hodgkinson and Greenaway seem to have faithfully carried out this conscientious purpose of the author.

It is not necessary to attempt here any statement of the method or classification of the book, as it would take more room than we can give, and, after all, would concern chiefly the special students of organic chemistry. The names upon the title-page are the best guarantee of the character of the volume, and an examination of its pages shows that it has been executed with remarkable clearness and accuracy. In regard to the formula? based upon the atomic theory which now play so prominent a part in organic chemistry, Professor Wislicenus admonishes students that they must be taken with great reserve. On this point he says: "In the present state of our science we can not neglect the frequent use of structural formulas based on the valency of the chemical elements. Their partial uncertainty and, in many points, tangible short-comings, need not prevent their use to some extent in a text-book, although their use requires care. With regard to the manner of writing the constitutional formulæ, no dogmatic adherence to any single method will be adopted, so that the formula of one and the same substance may be found varyingly written in different places. With every one of these systems of formulas there is the danger of substituting a concrete image in place of an idea. These images we certainly can not do without, but we must keep the idea lying behind such an image as far as possible pure, and also mobile, seeing that in comparison with older views we have in it only relative not absolute truth."

interesting monograph is an important practical contribution to what may be called the science of illusions. It is a