January 4, 1918] 



SCIENCE 



23 



The skeleton of a freshly killed animal is more 

 or less carefully cleaned of muscles and em- 

 bedded in a plain agar solution (15 gm. per 

 liter of water) which has been cooled to the 

 pouring temperature (43° to 45° C.)- The 

 medium is allowed to solidify and the prepara- 

 tion is covered and set away at room tempera- 

 ture. The digestion requires from ten days 

 to several weeks, depending largely on the ex- 

 tent of the preparatory cleaning. The time 

 may be reduced by the use of incubator tem- 

 perature. We have tried inoculating the skele- 

 tons with cultures of anaerobic proteolytic 

 bacteria, but without great advantage. 



The medium absorbs much of the odor and 

 with suitably covered dishes it has been pos- 

 sible to leave the cultures standing in the 

 laboratory. When the digestion is completed 

 the bones can be conveniently dissected from 

 the medium in their original relations. Wash- 

 ing the parts as removed completes the process. 

 The skeletons thus prepared are very white, 

 and bleaching is usually xmnecessary. The 

 method is best adapted to small skeletons, 

 which can be embedded easily. It is these, 

 however, which present the greatest liability to 

 loss of parts in a fluid medium. The method 

 promises to be particularly useful in the study 

 of the cartilaginous skeletons of embryos. 

 Ealph G. Hurlin 



BiOLOoicAL Laboratory, 

 Clark College 



SHALL THE USE OF THE ASTRONOMICAL DAY 

 BE DISCONTINUED? 



To THE Editor of Science : The question 

 has recently been raised in England whether 

 the astronomical day should not be set back 

 twelve hours, so as to begin at midnight 

 instead of at noon. It is stated by those ad- 

 vocating the change that the practical con- 

 sideration of those using the Nautical Al- 

 manacs should prevail as against the usage of 

 astronomers. The opinion of American 

 astronomers has been requested and a com- 

 mittee of the American Astronomical Society 

 has been appointed to collect information for 

 presentation at the next meeting of the So- 

 ciety. 



The committee desires to obtain an expres- 



sion of opinion on this subject from as large 

 a number as possible of astronomers, geodesists, 

 surveyors, navigators, and all others who have 

 occasion to use Nautical Almanacs. 



Communications may be sent direct to Pro- 

 fessor W. S. Eichelberger, Director of the 

 Nautical Almanac, U. S. Naval Observatory, 

 Washington, D. C, or possibly better to some 

 journal, where a public expression of opinion 

 may stir up further discussion. 



W. S. Eichelberger, 



Chairman 



SCIENTIFIC BOOKS 



The Microscope. By Snio.v Henry G.\ge, Pro- 

 fessor of Histology and Embryology, Emeri- 

 tus in Cornell University The Comstock 

 Publishing Company, 1917. Twelfth edi- 

 tion, 472 pages, 252 text figures. 

 This standard work is so well known to 

 American students that extended comment 

 u]X)n its usefulness or upon its special merits 

 is superfluous. The twelfth edition has been 

 more extensively revised and rewritten than 

 any one of the earlier ones. While many new 

 things are presented, nothing has been consid- 

 ered which the author has not personally 

 tested and found practical. Among the more 

 important new devices described are: (1) the 

 single objective binocular for both high and 

 low powers; (2) improved apparatus for draw- 

 ing with the projection microscope; (3) per- 

 fected ray filters which make it possible to get 

 photomicrographs of almost any microscopic 

 specimen ; (4) the use of '' daylight " glass in 

 microscopical illumination, and (5) the dark 

 field illumination for all powers which makes 

 it possible to study living structures in much 

 greater detail than heretofore. Some subjects 

 treated in the previous edition, such as metal- 

 lography and microchemistry, which are now 

 presented adequately in other available works, 

 have been omitted. Because of its clearness 

 and accuracy of statement, its well-chosen ma- 

 terial, and its wealth of information, the book 

 will without doubt continue to be the most 

 widely used volume on the microscope in 

 American laboratories. 



M. F. GUYER 



