WITH THE MICROSCOPE. I(X) 



199. The Author's Carmine Fluid for staining the germinal matter 

 is made as follows : 



Carmine, 10 grains. 



Strong liquor ammonias, | drachm. 



Price's glycerine, 2 ounces. 



Distilled water, 2 ounces. 



Alcohol, ^ ounce. 



The carmine in small fragments is to be placed in a test tube, and 

 the ammonia added to it. By agitation, and with the aid of the heat 

 of a spirit-lamp, the carmine is soon dissolved. The ammoniacal 

 solution is to be boiled for a few seconds and then allowed to cool. 

 After the lapse of an hour, much of the excess of ammonia will have 

 escaped. The glycerine and water may then be added and the 

 whole passed through a filter or allowed to stand for some time, and 

 the perfectly clear supernatant fluid poured off and kept for use. 

 This solution will keep for months, but sometimes a little carmine is 

 deposited, owing to the escape of ammonia, in which case one or two 

 drops of liquor ammonias may be added to the four ounces of 

 carmine solution. 



The rapidity with which the colouring of a tissue immersed in this 

 fluid takes place, depends partly upon the character of the tissue and 

 partly upon the excess of ammonia present in the solution. If the 

 solution be very alkaline the colouring will be too intense, and much 

 of the soft tissue or imperfectly developed formed material around 

 the germinal matter, is destroyed by the action of the alkali. If, on 

 the other hand, the reaction of the solution be neutral, the uniform 

 staining of tissue and germinal matter may result, and the appear- 

 ances from which so much may be learnt are not always produced. 

 V/hen the vessels are injected with the Prussian blue fluid the 

 carmine fluid requires to be sufficiently alkaline to neutralise the free 

 acid present. The permeating power of the solution is easily 

 increased by the addition of a little more water and alcohol. In 

 some cases the fluid must be diluted with water, alcohol, or glycerine, 

 and the observer must not hastily condemn the process, or conclude as 

 some have, that a particular form of germinal matter is not to be coloured 

 until they have given the plan a fair trial and tried a few experiments. 

 Notwithstanding the advantages of the above plan and its success 

 in the hands of many observers, objections have been urged against 

 it by some who, I venture to think, have not made themselves 

 familiar with the details of the method. It has been said that the 

 formed material may be stained as well as the germinal matter. As 

 every one must know, almost any tissue may be stained. Hair, horn, 

 wool, paper, &c., may be deeply dyed, even after they have been 





