and Laboratory Methods. 1735 



diameters have been made without reaching the Umit of the illuminating power 

 afforded by an apparatus admitting a beam of sunlight four and one-half inches 

 in diameter. When it is remembered that a magnification of 10,000 diameters 

 means that the area of the picture on the screen is 100,000,000 times the area of 

 the object, the enormous power of sunlight is still more evident. If it were not 

 for its limitations, sunlight would be the ideal for all projection work, as it is, in 

 fact, a necessity, for very high-power projection. A thin cirrus cloud or consid- 

 erable smoke in the lower stratum of the atmosphere reduces the solar power to 

 that of the electric arc ; heavier smoke or thicker clouds reduces it through all 

 degrees to below the minimum power for projection work. For about two hours 

 after sunrise and the same time before sunset there is a marked reduction of 

 power, varying with the condition of the atmosphere. Solar projecting apparatus 

 should be placed in windows facing easterly, westerly, or preferably toward the 

 south, where it will receive the unobstructed rays of the sun, thus limiting still 

 further its availability. But in spite of all these limitations, the ease with which 

 sunlight is used, its noiselessness, its steadiness when there is a clear sky, its 

 great power and the small cost of necessary apparatus render it a very desirable 

 light for projection work in school-rooms. 



With a solar or electric arc projection microscope in a biological laboratory 

 many difficult problems for beginners in microscopy are solved at once, the 

 students' work is made more definite, the most typical slides prepared by the 

 class or by the teacher may be exhibited for the benefit of all, and an endless 

 variety of animal and plant species may be shown in such a way as to awaken 

 interest, stimulate inquiry, and broaden knowledge gained by ordinary micro- 

 scopical work, lectures, and reading. A. H. Cole. 

 University of Michigan. 



A New Preservative Fluid. — In a recent number of the Lancet (161 : 

 1334, 1335, Nov. 16, 1901) Gait gives the results of a series of experiments 

 extending over several years, having as its object the discovery of a preservative 

 fluid which would preserve the natural colors of anatomical specimens, and at the 

 same time be free from some of the objectionable features of the well known 

 Kaiserling's fluid. The fluid which was finally found to give the best results 

 has the following formula : 



Common salt - - - 5 oz. Chloral hydrate - - 1 oz» 



Potassium nitrate - - - 1 oz. Water - - - - 100 oz. 



Before being put into this solution for permanent preservation the tissues 

 must undergo some preliminary treatment. The fresh tissue or specimen is 

 washed for several hours in running water, and then fixed or '' set " in an excess 

 of methylated spirit. In case of large or soft specimens the addition of .5 per 

 cent, of formalin accelerates the fixing of the tissues. The length of time which 

 must be taken for this fixing process varies from six hours to a week according 

 to the size and nature of the specimen. From this fixing bath the specimen is 

 transferred directly to the preservative fluid. It may float in this for a short 

 time before becoming thoroughly permeated. In some cases it was found neces- 

 sary to renew the fluid after two or three weeks. After this no care is neces- 

 sary except to replenish the jars with water, to make up for the loss by evapora- 

 tion, in case the preparation is not sealed. 



Advantages claimed by the author for this fluid are: 1. Its cheapness. 2. 

 The simplicity of the process. 3. Specimens may be kept in the light without 

 effect on the preservation of color. 4. Color preservation is better than in the 

 older methods. 5. Its portability, requiring only the carrying of the solid 

 ingredients. 6. It is non-volatile, non-poisonous, and non-irritating. 7. Its 

 action on the cellular elements of the tissue is negative. 8. It causes only very 

 slight shrinkage of the specimen. Raymond Pearl. 



