240 



THE AMERICAN MONTHLY. 



[December. 



both sets of lines together, so that it is 

 possible to set the graduated screw-head 

 at zero for any particular measurement. 

 This is a very convenient as well as useful 

 feature. 



CORRESPONDENCE. 



About Magnification. 



To THE Editor : — Being somewhat in- 

 terested in the article on page 203, ' The 

 Magnifying Power of an Inch Objective,' 

 I wish to propound the following ques- 

 tions : — 



First. What is the magnifying power of 

 an inch lens at 10 inches between object 

 and lens ? 



Second. What is the formula of a two- 

 inch eye-piece as used in the microscope; 

 not in the telescope ? 



Third. What is the magnifying power 

 of a two-inch eye-piece, 10 inches between 

 object and diaphragm ? 



Fourth. Are there fifty microscopes in 

 this country that are furnished with two- 

 inch eye-pieces ? 



Fifth. What is the length of a ten-inch 

 tube ? 



Any person who has used the micro- 

 scope for only a few days will doubtless 

 think himself able to answer any one of 

 the above questions. I want the actual 

 measurements. 



Walter H. Bulloch. 



[Our columns are open for replies to 

 any of these questions. Evidently Mr. 

 Bulloch has been studying this subject of 

 magnification, and now desires to draw 

 out some ideas from others. The ques- 

 tions are worthy of careful consideration. 

 —Ed.] 



NOTICES OF BOOKS. 



Methods of Research in Microscopical An- 

 atomy and Einbryolos^y. By Charles 

 Otis Whitman, M. A., Ph. D. Illus- 

 trated. Boston : S. E. Casssino & 

 Company. 1885. (8vo, pp. viii and 

 255) 



Dr. Whitman's admirable manual is 

 undoubtedly the most practical treatise 

 on the'ubjects with which it deals at pres- 

 ent accessible to the student who wishes 

 to know how to prepare his materials 

 properly for staining, and how to imbed, 

 section, and mount delicate objects and 

 tissues in accordance with the most recent 

 and approved methods. These methods 

 which have been developed by the work- 



ers in the laboratories of continental 

 Europe, and have been still further im- 

 proved upon by the untiring efforts of the 

 corps of investigators gathered together 

 at Naples, under the direction of Dohrn, 

 are fully explained in this book. While 

 the work deals very largely with the 

 methods pursued by the embryologist, the 

 working histologist and anatomist cannot 

 fail to be instructed by reference to its 

 pages. It is, in fact, a laboratory manual, 

 explaining clearly the steps by which de- 

 finite results are to be reached. It is not 

 a mere collection of formulae, but a trea- 

 tise by the aid of which the student may 

 instruct himself in that comparatively 

 new art, microtomy, which is revealing 

 so much that is of importance in modern 

 biology. It discusses general and special 

 methods, the enlarged stereogrammatic 

 reconstruction of minute objects from 

 serial sections, the times and places of 

 ovulation of a considerable variety of 

 forms, fixatives, and gives full directions 

 for successfully cutting serial sections. 

 Formulas for the preparation of reagents 

 are given, and two very useful micromet- 

 ic tables complete the book. There is 

 a good index. Nothing is said of micro- 

 scopes and accessories, and their con- 

 struction or theory. The methods useful 

 to the actual investigator are alone dealt 

 with, leaving the work unencumbered 

 with details which have already beon 

 capably handled by Carpenter in his 

 hiadbook. J. A. R. 



RechercJies Anatoniiques sur les Organes 

 Ve ^i'atifs de r Urtica Dioica. L. Par 

 A. Gravis, Docteur en Sciences Natu- 

 relles, assistant du cours de botanique 

 a rUniversii^ de Liege, Seci^ aire de la 

 Soc e i Beige de Microscopie. Brux- 

 elles ; Libraire MeJicale et Scienti- 

 fique de A. Manceaux, 1885. (4°, pp. 

 232, plates 23, with explanations.) 

 An adequate review of this valuable 

 work would require more space than can 

 be here given to the subject. In the in- 

 troduction the author concisely states his 

 object in preparing the memoir, which 

 was to present an anatomical study of the 

 vegetative organs of a plant throughout its 

 whole extent and in all stages of growth. 

 The result is a knowledge of the variations 

 of structure which these organs undergo. 

 The structure of the plant has been 

 thoroughly studied and described in detail, 

 with the aid of beautifully drawn figures. 

 We have not even space in which to give 

 a summary of the results, but must refer 

 botanists to the original work, which will 

 reward careful study. 



