On Preparing Tissues for Examination. 13 



3. Dilute Spirit. Many tissues can be hardened in 

 spirit alone if they are placed in dilute spirit at first, 

 so that the elements of which they are composed are 

 not shrunk. This process is also used after hardening 

 by any of the others. 



Dilute spirit is made by adding 1 part of water to 

 2 parts of methylated spirit. 



The material to be hardened should not be left in 

 this mixture more than from 24 48 hours. 



It is then transferred to pure methylated spirit. 



4. Bichromate of Potash. Make a 2 per cent, solution 

 and keep it on hand, as it is very useful for many tis- 

 sues that require slow hardening. A solution can be 

 made much more quickly with warm water than cold. 

 This solution is also very useful to place portions of 

 morbid material in, on their removal from the body in 

 the post-mortem room, they can afterwards be trans- 

 ferred to the chromic acid mixture for more rapid hard- 

 ening. This solution takes from three to seven weeks 

 to harden according to the size of the specimen, and the 

 frequency with which the solution is changed. 



5. Bichromate of Ammonia. A 2 per cent, solution is 

 used in precisely the same manner as the former, and 

 is applicable to the same tissues. 



6. Chr ornate of Ammonia. Make a 5 per cent, solu- 

 tion, that is 1 oz. of the salt to 20 oz. of water, and 

 filter. Keep it in a stoppered bottle. When this harden- 

 ing agent is used for fresh tissue, such as mesentery, a 

 small quantity is placed in a glass vessel and the tissue 

 immersed in it for 24 hours, it is then washed until no 

 more colour comes away and mounted in glycerine. 



