STAINING, PRACTICAL AND THEORETICAL 



Objects fixed in liquids other than alcohol may be stained by this 

 method provided they are soaked in 90% alcohol for at least three 

 days. The best preparations are made with fish, but amphibia and 

 mammals have also been tried with a fair degree of success, although 

 there is not the same firm consistency about the flesh of a mammal 

 or amphibian, prepared by this technique, as there is with that of 



a fish. 



The technique is particularly suitable for demonstratmg 



developing bone. 



Reference: Dawson, A. B. (1926). 



William's modification of Dawson's method 



This technique is particularly suitable for mammalian embryos 

 and mature specimens of Urodele amphibians; for distinguishing 

 between bone and cartilage and for demonstrating the relative 

 amount of ossification. 



The removal of the viscera is unnecessary in the case of museum 



specimens. 



Solutions required: 



A. Toluidine Blue 0-25 gm. 



Alcohol 70% 100 ml. 



Hydrochloric acid 0-5% • • 2 ml. 



Allow the solution to stand for twenty-four hours; 

 then filter and store in a tightly corked bottle. 



B. Potass, hydroxide 2% aqueous . . 



C. Alizarin Red, S o-ooi gm. 



Potass, hydroxide 2% aqueous . . 100 ml. 



(This solution should be freshly prepared.) 



D. Methyl salicylate 25% in cellosolve 



E. Methyl salicylate 50% in cellosolve 



F. Methyl salicylate 75% in cellosolve 



Technique: 



1. Wash specimens for twenty-four hours in 70% alcohol con- 

 taining o-2% of concentrated ammonia solution. 



2. Stain for seven days in Solution A. 



3. Harden and destain for seventy-two hours in four changes of 

 95% alcohol. 



126 



