268 PRACTICAL MICROSCOPY. 



with the size, poured into a tin vessel placed in hot water, 

 and strained through fine muslin into another, just before 

 it is required to be used. It must not be forgotten that 

 when size is used, the preparation to be injected must be 

 steeped in hot water, and kept warm until the operation is 

 finished. 



Opaque injections in various colours often form very 

 instructive objects. An injection of the liver illustrates 

 this very well : the artery may be injected with vermilion, 

 the portal vein with white lead, the duct with Prussian 

 blue, and the hepatic vein with lake. A section of an 

 injected kidney, with Prussian blue and lake, is also a 

 pleasing slide when well performed. 



After all, opaque injections have but a limited scientific 

 value, and therefore the student is advised to utilise his 

 energies upon the transparent class, as they can be 

 examined with all powers, and when preserved in fluids 

 the most delicate structures retain their integrity. 



The Prussian blue fluid for transparent injections is 

 made as follows (Beale) : 



Glycerine i oz. 



Alcohol i oz. 



Ferrocyanide of potassium 12 grains. 



Tinct.ferriperchlor I drachm. 



Water 407. 



The ferrocyanide is to be dissolved in an ounce of the 

 water and the glycerine added, while the Tinct. ferriper- 

 chlor. is separately mixed with another ounce of the water. 

 These two solutions should now be mixed very gradually, 

 and well shaken, the iron being added to the ferrocyanide ; 

 the mixture of spirit with the remainder of the water must 

 now be added very gradually, when the fluid is ready for use. 



Dr. Beale's carmine fluid is made in the following 

 manner : 



