Staining Animal Sections 145 



fectly rectangular blocks are formed ready for fixing to the 

 brass cap at the end of the arm of the microtome, which 

 is filled with paraffin ; this should be warmed over a spirit- 

 lamp, and the block containing the specimen is to be 

 pressed against the melted paraffin until it adheres firmly. 



LESSON III. 



STAINING ANIMAL SECTIONS AND MOUNT- 

 ING IN CANADA BALSAM. 



All sections of organs and tissues should be stained with 

 some colouring reagent, so that their structure may be 

 made more apparent. Certain parts of the tissue have a 

 special affinity for the dyes or stain ; they therefore become 

 more deeply tinted, and stand out clearly from the sur- 

 rounding tissues. 



The following staining reagents are the most useful : 



Grenacher's Alcoholic Borax Carmine. — Carmine 

 3 grammes ; borax 4 grammes ; distilled water 100 c.c. 

 Dissolve the borax in the water, add the carmine, and 

 apply gentle heat until all is dissolved ; then add 100 c.c. of 

 70 per cent, alcohol, filter, and keep in a stoppered bottle. 



Staining Process. — (1) Place the section in distilled 

 water to wash away the alcohol, then place a little of the 

 carmine in a watch-glass, and immerse the section for from, 

 three to five minutes. 



(2) Wash the section in methylated spirit. 



(3) Take of methylated spirit 5 parts, and of hydrochloric 

 acid 1 part, and mix them well together. A quantity of 

 this acid solution may be made up and kept ready for use 

 at any time. 



Immerse the section in the above, and leave it to soak for 

 about five to ten minutes, or, if overstained, until the desired 

 tint is obtained. Sections of skin and scalp may be left 

 until all colour is removed from the fibrous tissues; the 



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