136 THE FROG CHAP. 



PRACTICAL DIRECTIONS 



Materials required for the Preparation and Sectioning 

 of Animal Tissues. In addition to the requisites mentioned 

 in Chapters I and VII, the following will be required : 



a. Corrosive sublimate : a saturated solution in water. 

 Care should be taken in using this solution, as it is a very 

 virulent poison. 



b. Absolute alcohol. 



c. Turpentine or xylol. 



d. Paraffin : " hard " and " soft." Get an ounce or two 

 of each. 



e. A solution of Canada balsam in chloroform, xylol, or 

 turpentine. This should be kept in a small glass bottle with 

 a ground glass cap not a stopper or cork. 



/. A solution of alcoholic borax carmine. This (like many 

 other useful staining-solutions, such as Ehrlich's hcematoxy- 

 lin) may be bought ready prepared : or it may be made as 

 follows : Grind up in a mortar 2 grammes of carmine and 

 4 grammes of borax, and dissolve in 100 c.c. of distilled 

 water : to this solution add an equal volume of 70 per cent, 

 alcohol : allow to stand for a day or two and filter. 



g. A water-bath, in which melted paraffin may be kept at 

 a constant temperature. For a makeshift you can use a 

 saucepan with a flat piece of tin over it : fill the saucepan 

 about half full of water, and heat it over a spirit-lamp or a 

 small oil-lamp or gas-burner, regulating the distance of the 

 flame so as to keep the temperature of the water at about 

 5 5C.(i5iF.). 



h. Two or three watch-glasses or other small shallow 

 vessels for containing melted paraffin. 



i. A sharp, flat-ground razor. 



j. A section-lifter, made by beating out flat about half an 

 inch of the end of a piece of stout copper wire, about 6 in. 

 long, and bending the flattened portion at an obtuse angle 

 with the rest. 



Preparation of Tissues for Section-Cutting. 



a. Fixing, hardening, and decalcifying. 



Sections may be cut from specimens which have been care- 

 fully preserved in alcohol : first in 70 per cent., and after 

 a day or two transferred to 90 per cent. But certain other 

 reagents are more effective for the purpose of fixing the 



