APPENDIX TO THE HISTOLOGICAL SECTION. 109 



IP.C. 10 parts, water 55 parts. Small pieces take from 2 to 24 hours, 

 followed by thorough washing in water and after-hardening in alcohol. 



10. Platino-aceto-osmic fluid (Hermann's solution). Platinic 

 hloride IP- C - 15 parts, glacial acetic acid 1 part, osmic acid 2 P- C - 2 or 4 

 parts. This fluid does not produce "artificial" networks in protoplasm. 

 Time and after-treatment same as 9. 



11. Mullep's fluid. Dissolve 25 potassium bichromate and 10 ? 

 sodium sulphate in one litre of water. Change the fluid on the 2nd, 

 4th, 6th, and 14th days. Six to eight weeks are required to produce 

 the necessary toughness. This is one of the best penetrants and a 

 reliable reagent. After-treatment with alcohols in the dark until dis- 

 coloration ceases. 



12. Muller and spirit. 3 parts of Miiller, 1 part of spirit (methy- 

 lated). Let the mixture cool before use. After 3 days, change to 

 bichromate of ammonia 2 i xc - solution. Hardening is sufficient in about 

 three weeks. The after-treatment is the same as for Muller. A good 

 general reagent. This mixture forms the first step in Hamilton's method 

 for hardening large masses of brain. Keep from the light and use 

 fresh. 



13. Osmic acid. This reagent is an instantaneous fixer, and has 

 been regarded as devoid of any distorting effect upon tissues. It pene- 

 trates so slowly that only very small pieces of tissue can be treated. 

 As a fixing and hardening reagent it is used for nerves whose medullary 

 sheaths it is desired to recognise. 1 P- C - solution in water 24 to 48 hours, 

 followed by strong alcohol if sections are required. Cut in paraffin. Its 

 vapour from a 2i ) - c - solution has been employed for fixing glandular 

 tissue (Langley). It is most!} 7 used in conjunction with other agents, 

 or upon sections of already fixed and hardened tissues to stain fat, which 

 it turns black and for which 0'5 to 1 P- C - solutions are used, 12 to 24 hours. 



14. Bone-softening* fluids. 



(a) Chromic acid 12 , HX0 8 25 cc , water to 1000 cc for decalcifying 

 bones, teeth, and hardening the soft parts at the same time. Followed 

 by alcohol treatment the same as 11 in the dark. 



(6) Picric and nitric (or sulphuric) acid. The former saturated in 

 water containing 2P- C - nitric acid. Chiefly useful for embryonic bones 

 and teeth. As soon as the lime salts are removed, after-hardening by 

 increasing alcohols is necessary. The picric acid should be completely 

 removed by the changes of alcohol. 



