94 HOW TO WORK 



acid is present in the fluid in which the specimen is preserved. I 

 have many specimens injected with Prussian blue, which have 

 retained their colour perfectly for more than ten years. An advan- 

 tage of the Prussian blue over other fluids is, that the ingredients 

 required to make it are very cheap, and can be readily obtained 

 everywhere. Capillaries injected with the Prussian blue fluid under 

 high magnifying powers are represented in pi. XXV. 



I would most earnestly recommend all who are fond of injecting 

 to employ transparent injections, and to endeavour by trying various 

 transparent colouring matters, to discover several which may be 

 employed for this purpose, for I feel sure that by the use of carefully 

 prepared transparent injecting fluids, many new points in the anatomy 

 tissues will be made out. 



179. Turnbiiirs Blue. My friend, Mr. B. Wills Richardson, of 

 Dublin, has introduced Turnbull's blue in preference to ordinary 

 Prussian blue. Ten grains of pure sulphate of iron are to be dissolved 

 in an ounce of glycerine, or better, in a little distilled water and then 

 mixed with glycerine, and thirty-two grains of ferridcyanide of 

 potassium in another small proportion of water, and the solution 

 mixed with glycerine. These two solutions are then gradually 

 mixed together in a bottle, the iron solution being added to that of 

 the ferridcyanide, and mixture ensured by frequent agitation. The 

 other ingredients are added as in the Prussian blue fluid. This 

 modification may be adopted in all cases in which I have recom- 

 mended the ordinary Prussian blue. The proportions given in the 

 text are, however, unnecessarily large, and I find that the following 

 makes a good fine injecting fluid. 



Ferridcyanide of potassium ... ... 10 grains. 



Sulphate of iron ... ... ... 5 



Water ... ... ... ... i ounce. 



Glycerine (Price's) ... ... ... 2 ounces. 



Alcohol ... ... ... ... i drachm. 



The iron, dissolved in a little water and mixed with glycerine, is 

 to be added to the solution of the ferridcyanide, as in the prepara- 

 tion of the other fluid. 



iso. carmine injecting Fluid. In the hands of Mr. Smee, Pro- 

 fessor Gerlach, and others, a solution of carmine in ammonia has 

 long been employed for making minute injections with the most satis- 

 factory results. The solution may be diluted to the required tint 

 and injected. It is most applicable to injecting very delicate vessels, 

 as those of the brain ; indeed, if much force be employed, the fluid 



