WITH THE MICROSCOPE. 97 



A. A solution of bichromate of potash is made, in the propor- 

 tion of one part of salt to two of water. 

 B. A solution of nitrate of lead of the same strength. 



One part of solution A is placed in a small basin and mixed 

 with 4 parts of a concentrated solution of gelatine. Two parts of 

 solution B are placed in another basin and mixed with four parts 

 of jelly. 



These are to be slowly and thoroughly mixed together at a tem- 

 perature of from 75 to 90, and then heated in a water-bath at a 

 temperature of about 212 for half an hour or more. The mixture 

 is then to be carefully filtered through flannel. 



183. Of Injecting 1 Different Systems of Vessels with Transparent 

 injections. The transparent injecting fluids which may be used for 

 double injections, must have the same reaction. Thus the Prussian blue 

 fluid, and the carmine solution without gelatine, p. 95, maybe used for 

 this purpose ; but I have not yet been able to obtain other colours 

 which answer so well as these. Good transparent yellow and green 

 aad injecting fluids which might be used for double injections in 

 cases in which the Prussian blue fluid was employed, are much to be 

 desired. 



184. New Form of Soluble Prussian Blue. Briicke recommends 

 the following : 



Ferrocyanide of potassium, 217 grammes, dissolved in i litre of 

 distilled water. 



Perchloride of iron, 10 grammes in i litre of distilled water. 

 Sulphate of soda, a cold saturated solution. 



One volume of each of the two first solutions is to be mixed with 

 one volume of the soda solution. The iron and soda solution is then 

 to be mixed gradually with the ferrocyanide and soda solution with 

 constant stirring. The mixture is to stand for some hours, and the 

 deposit collected on a filter. The deposit is then washed with small 

 quantities of distilled water, until the filtrate runs through quite blue. 

 The blue powder thus prepared is quite soluble (?) in distilled water. 

 Briicke recommends that this be made into an injection with sufficient 

 gelatine to ensure it setting into a jelly. After injection the prepa- 

 ration is to be thrown into spirit, and then hardened in 90 per cent. 

 of alcohol ! a process which it may be remarked will effectually 

 destrcy many delicate structures, and entirely alter all. Briicke states 

 that the fluid bears chromic acid and bichromate of potash well, but 

 i,ays that all fluids containing glycerine must be carefully avoided ! 



H 



