THE PREPAKATION OP ANIMAL TISSUES. 51 



and preserve in common alcohol till required. A 

 small piece of this, stained in picro-carmine and 

 mounted in Farrant's medium, shows the above- 

 named structure beautifully. The fibres of white 

 fibrous tissue may be shown to advantage, thus : 

 Tear off fine strips of tendo achilles of an animal 

 and place them for twenty-four hours in the solu- 

 tion. By " teasing " a little piece in water the 

 white fibres held together by cement substance are 

 well displayed. 



Osmic Acid. 



This is purchased as a 1 per cent, solution and 

 diluted with distilled water to a ^, a J per cent, 

 solution, &c., as required. It is a hardening agent 

 which also stains fatty matter, and is, therefore, 

 useful in blackening the medullary nerve fibres. It 

 is very poisonous, very expensive, and soon spoiled 

 by exposure to light. It must be kept in a well 

 stoppered bottle, which should be of black glass or 

 covered with black paper, so that not a particle of 

 light shall be admitted. Substances placed in it 

 harden in from four to thirty-six hours, and may be 

 prepared and mounted in either glycerine, glycerine 

 jelly, or Farrant's medium. Very little pieces, not 

 larger than half a grain of wheat, are to be used of 

 any tissue, and the bottle in which they are placed 

 must also be very small ; the short glass tubes in 

 which homoeopaths keep their smallest pilules 

 answer well. 



With the above cautions and directions we may 

 enumerate the tissues which are treated with 

 advantage by osmic acid. In a 1 per cent, solution 



