125 



In the case of specimens with which it is advantageous to have 

 more information at hand a second label may be placed upon the 

 other end of the slide, and it may bear the following information : 



(1) Mode of fixation. 



(2) Imbedding method. 



(3) Stains employed. 



(4) Mounting medium (generally not necessary). 



(5) Special purpose of the preparation. 



A catalog giving the full data of the specimen, age, condition 

 of the animal, mode of preparation in detail, special points illus- 

 trated, etc., is not required for the preparations in this course, but 

 is valuable particularly in special investigations and with standard 

 specimens. 



CLEANING SLIDES AND COVER-GLASSES. 



114. Cleaning cover-glasses. Fill the large glass box 

 one-half full of cleaning mixture and put in the new covers, 

 one at a time, being sure that they are entirely immersed and the 

 cleaning mixture reaches all points. The one cover may be pushed 

 under by the next. Let them remain over night (or longer) and 

 then wash them thoroughly in running water, until all trace of the 

 cleaning mixture is removed. Then place the covers in 50 or 6j% 

 alcohol. 



115. Wiping the cover-glasses. When ready to wipe the 

 cover-glasses, remove several from the alcohol and put them on a 

 soft, dry cloth, or on some of the lens paper to let them drain. 

 Grasp a cover-glass by its edges, cover the thumb and index finger 

 of the other hand with a soft, clean cloth, or some of the lens paper. 

 Grasp the cover between the thumb and index finger and rub the 

 surfaces. In doing this it is necessary to keep the thumb and index 

 well opposed on directly opposite faces of the cover so that no strain 

 will come on it, otherwise the cover is liable to be broken. 



When a cover is well wiped, hold it up and look through it to- 

 ward some dark object. The cover will be seen partly by transmit- 

 ted and partly by reflected' light, and any cloudiness will be easily 

 detected. If the cover does not look clear, breathe on the faces and 

 wipe again. If it is not possible to get a cover clear in this way it 

 should be put again into the cleaning mixture. When the covers 



