722 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(6) Miscellaneous. 



Principles of Microscopy : being a Handbook to the Microscope.* 

 This book fills a gap in the literature of the subject, inasmuch as it is 

 written for the information and guidance of microscopists, to whom the 

 theory of the instrument with which they work is a matter of practical, 

 as distinguished from speculative interest. Although the undulatory 

 theory and the mathematical analysis of light pervade the work, they 

 are never suffered to become either the subject-matter of discussion or 

 its medium. The author absolutely eschews the " inarticulate " method 

 of expression by means of mathematical signs, with the result that the 

 book is a literary work from end to end. Notwithstanding the abstruse 

 nature of many of the problems attacked, it is readable by everybody, 

 mathematician or not, to whom the Microscope is practically familiar. 



The work is divided into two parts. The first part deals with the 

 "object picture," a term used to denote the object under that aspect 

 which furnishes a picture to the eye. Object pictures are classified 

 under four beads — as " outline pictures, colour pictures, outline and 

 colour pictures, and pictures in relief." The advantages and dis- 

 advantages which attach to these various kinds of images — considered 

 as means of revealing the form and structure of objects — and their 

 liability to originate false impressions, form the subject matter of the 

 first chapter. The next three chapters of the first part are devoted to 

 the examination of the practical consequence deducible from the 

 principles developed in the first chapter, and in these the theory and 

 practice of illumination, mounting, and staining are successively dis- 

 cussed, while the fifth chapter sums up the whole result, and points the 

 moral of what has preceded. These five chapters together thus form a 

 treatise upon the preparation and exhibition of transparent objects in 

 the Microscope, with special reference to such objects as occur in the 

 course of medical practice and research. 



The second part is much the larger part of the book, and is devoted 

 to the image formed by the Microscope. This part of the work, there- 

 fore, covers more familiar ground than the first, since all the text- 

 books which treat of the theory of the Microscope deal with this 

 subject. The mode of treatment is, however, in this part equally 

 original, and an impression which the author is very successful in leav- 

 ing on the mind of his reader is that there is nothing occult about the 

 theory of the Microscopic image. The optical laws involved, even where 

 high magnification is concerned, are all illustrated by experiments which 

 can be made with low-power lenses and large scale objects. The notion 

 that microscopic vision is something sui generis finds here no quarter. 



Ten chapters are devoted to this division of the work. The first 

 of these — the sixth chapter of the book— is devoted to the discussion 

 of images formed by simple apertures, from which the general laws of 

 image-formation are very ingeniously deduced, and the main ideas, 

 such as magnification, illumination, definition, and resolution — with 

 which the reader is concerned to become familiar — are easily intro- 



* By Sir A. E. Wright, M.D. F.R.S. London : Archibald Constable and 

 Co., Ltd., 1906, xxii. and 250 pp., 18 pis. and 97 figs, in text. 



