I3 6 THE FROG CHAP. 



b. Absolute alcohol. 



c. Turpentine. 



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



e. A solution of Canada balsam in chloroform or turpentine. This 

 should be kept in a small glass bottle, with a ground glass cap not a 

 stopper or cork. 



f. A solution of alcoholic borax-carmine. This (like many other useful 

 staining-solutions, such as Ehrlich's hamatoxyliri) 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 loo 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 make-shift 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 55 C. (131 F.). 



h. Two or three watch-glasses or other small shallow vessels for con- 

 taining melted paraffin. 



i. A sharp, flat-ground razor. 



i. 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 carefully pre- 

 served in alcohol : first in 70 per cent. , and after a day or two trans- 

 ferred to 90 per cent. But certain other reagents are more effective for 

 the purpose vi fixing the tissues i.e., quickly killing and coagulating 

 the protoplasm of the cells with a minimum of shrinkage, and of these 

 the one most generally useful is a solution of corrosive sublimate (see a, 

 above), in which, from a freshly-killed frog, place small pieces of the 

 various organs and tissues to be examined e.g., skin, intestine, stomach- 

 liver, pancreas, kidney, ovary, spermary, and spinal cord, as well as 

 the inner half of the eyeball. The intestine and stomach should be 

 first washed out in salt-solution, and then cut into pieces about f inch 

 long ; the liver should be cut into pieces not more than inch cube. 

 After about half-an-hour to two hours, according to the size of the 



