Hardening Animal Tissues for Examination. 71 



ferred, but it has a tendency to shrink some tissues too 

 much. It hardens in about ten days. Change the spirit 

 every twenty-four hours for the first three days. Suitable 

 for skin, scalp, testicle, penis, prostate gland, vas deferens, 

 epididymis, ovary, uterus, Fallopian tubes, placenta, mam- 

 mary gland, supra-renal glands, tonsils and all injected 

 organs. 



Decalcifying Solution. For bones and teeth. Make a 

 l-6th per cent, watery solution of chromic acid, and for 

 every ounce add 5 drops of nitric acid. This fluid will 

 soften the femur of a dog in about three weeks ; larger 

 bones will take longer. Change the fluid several times, and 

 test its action by running a needle through the thickest 

 part of the bone. If it goes through easily, the bone is soft 

 enough ; if not, continue the softening process a little longer. 

 When soft enough transfer to water, and soak for an hour 

 or two ; then pour off the water and add a 10 per cent, 

 solution of bicarbonate of soda, and soak for twelve hours to 

 remove all trace of acid. Wash again in water, and place 

 in methylated spirit until required. Bones and teeth 

 should always be softened in a large quantity of the decal- 

 cifying solution. 



General Directions for hardening Tissues. 



1. Always use fresh tissues. 



2. Cut the organs into small pieces with a sharp knife. 



3. Never wash a specimen in water ; when it is necessary 



to remove any matter, allow some normal salt 

 solution to flow over the surface of the tissue, or 

 wash in some of the hardening reagent you are 

 going to use. 



4. All specimens should be hardened in a large quantity 



of the reagent ; too many pieces should not be 

 put into the bottle, and they should be kept in a 

 cool place. 



5. In all cases the hardening process must be completed 



in spirit. 



