MOUNTING AND PEEPAEATION OF OBJECTS. 69 



When forming an opinion, the condition of the 

 tissue, as regards its age, (embryonic tissues stain- 

 ing very readily), its hardness, the alkalinity of the 

 solution, and the magnifying power required to show 

 it properly should all be taken into consideration. 

 For further particulars we refer to Beale's " How to 

 Work with the Microscope," etc. ; with this caution 

 that all blue and violet staining solutions are useless, 

 unless the operator has unlimited time at his dis- 

 posal for the modification of the photographs by 

 various methods of intensification, after their direct 

 production. 



If the sections are thin and intended for minute 

 investigation, they are removed from the carmine 

 solution by the flat spoon and placed for a short 

 time in equal parts of distilled water and alcohol, 

 this removes excess of colouring matter; they are 

 next transferred to glycerine and camphor water, 

 where they may be allowed to remain for a day or 

 two, (covered with a bell jar), before mounting, iu 

 gum and glycerine. If thick and only required for 

 very low powers, after removal from the carmine, 

 they are placed in absolute alcohol, for twenty-four 

 hours. When this period has elapsed each section 

 is taken up separately by the spoon, both are firmly 

 pressed between two folds of blotting paper held 

 between the finger and thumb, (no danger of injur- 

 ing the specimens need be apprehended, as they 

 have been considerably hardened by the alcohol), 

 and transferred to a saucer containing clove oil, in 

 which they are left for two or three hours, covered 

 by a bell jar as before. 



