Hardening and Preserving Animal Tissues 133 



and they should be cut into small pieces, so that the 

 alcohol may penetrate as quickly as possible. 



Change the alcohol every day for the first three days. 

 The hardening is usually complete in a week. 



Chromic Acid and Spirit. — Chromic acid \ per cent., 

 watery solution 2 parts, and methylated spirit 1 part. 

 This reagent hardens in about ten days. Then transfer to 

 methylated spirit, which should be changed every day until 

 no colour comes away from the tissues. It is suitable for 

 cartilage, nerve-trunks, heart, lips, blood-vessels, trachea, 

 lung, tongue, bladder, ureter, intestines, and oesophagus. 



Potassium Bichromate. — Make a 2 per cent, watery 

 solution. This will harden in about three weeks. Then 

 transfer to methylated spirit, and change the spirit every 

 day until no colour comes away from the tissues. It is 

 suitable for muscle, spleen, liver, and kidney. 



Ammonium Bichromate. — Make a 2 per cent, watery 

 solution. It hardens in from three to four weeks. Then 

 transfer to methylated spirit, and change every day until 

 no colour comes away from the tissues. It is suitable for 

 spinal cords, medulla, pons Varolii, cerebellum, and cere- 

 brum. 



Miiller's Fluid. — Bichromate of potash 30 grains, sul- 

 phate of soda 15 grains, distilled water 3| ounces. It 

 hardens in from three to five weeks. Then transfer to 

 methylated spirit, and change every day until no colour 

 comes away from the tissues. Suitable for lymphatic 

 glands, eyeballs, retina, and thymus gland. 



Methylated Spirit. — May be used universally, if pre- 

 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. Make a \ per cent. 



