46 THE MICROSCOPE 



KoUmann's Red Mixture is very useful. One gramme of 

 carmine, dissolved in a little water, with 15 to 20 drops of con- 

 centrated ammonia, and diluted with 20 c.cm. of glycerine. An 

 additional 20 c.cm. of glycerine is to be tempered with 18 to 20 

 drops of strong muriatic acid, and carefully added to the carmine 

 solution, at the same time shaking the latter strongly. It may be 

 subsequently diluted by the addition of about 40 c.cm. of water. 



Dr. Carter's Carmine.— There are several ways of making this 

 stain, but whichever way may be chosen the greatest care must be 

 exercised in making it a neutral, or slightly acid mass ; because, if 

 it be alkaline, it will diffuse through the vessels, and stain the 

 adjacent tissues, and render the preparation completely worthless. 

 The mass had better be slightly acid, but if too acid granulation 

 of the carmine takes place, and the fluid will not be driven into 

 the arterioles, much less the capillaries. Parts injected by a 

 carmine and gelatine mass must be immersed in equal parts of 

 water and methylated spirit, having i per cent, of acid in it. Take 

 of carmine 120 minims ; glacial acetic acid, 86 minims ; solution 

 of gelatine (gelatine, i part, water 6 parts), 2 ounces ; water, 

 ih ounces. Dissolve the carmine in the ammonia and water, with 

 the aid of a gentle heat, and filter ; add to this i J ounces of /lo^ 

 gelatine solution, and mix thoroughly. Add the acid to the 

 remaining | ounce of gelatine solution, and drop this into the 

 heated carmine mixture, with constant stirring. 



Dr. Stirling's Mass.— Take of carmine 60 grains ; strong 

 ammonia, 60 minims ; glacial acetic acid, 80 minims (about) ; 

 gelatine (Cox, or Coignets), i ounce ; water, q.s. Soak the 

 gelatine in water several hours ; pour off the water which is not 

 absorbed after the gelatine is completely swollen up, and melt it 

 in a water bath. Then strain while hot, through flannel, and make 

 up the solution to 2 ounces. Place the carmine in a mortar, and 

 add to it the ammonia and 2 ounces of water, and leave it for 

 12 hours. Then filter, and add acetic acid drop by drop, stirring 

 all the while, until the ammonia is completely neutralised. As the 

 ammonia becomes faint, the acid must be added very cautiously. 

 So long as there is free ammonia, the fluid is dull red, but 

 becomes a florid, bright colour the moment the ammonia is 



