•i2 THE MIGKOSCOPE 



(3) Natural injections ; or the introduction of pigments into 

 the circulation of living animals. 



This latter method is usually resorted to in cases where the 

 two preceding processes are either altogether impracticable, or very 

 difficult to perform ; as, for example, the filling of the bile ducts 

 throughout their course in the liver. 



The second method of injection is very convenient when time 

 cannot be spared to do the work by hand ; but the first method 

 (injection by hand with the syringe) is the one which should be 

 mastered on account of its simplicity when once learned, less 

 trouble, and the ease with which it can be performed. 



The substances used for making injections may be divided 

 into two classes : the first includes all those which are fluid at the 

 ordinary temperature ; while the other includes such as become 

 fluid only when heated, and return again to the solid form on 

 cooling; these are called "masses." 



Prussian Blue Fluid.— Glycerine, i ounce ; methylated spirit, 

 I ounce ; ferrocyanide of potassium, 1 2 grains ; tine, perchloride 

 of iron, i drachm ; water, 4 ounces. Mix together the glycerine, 

 water, and spirit, and divide the mixture into two equal parts. In 

 one part (a) dissolve the ferrocyanide, and to the other part {b) 

 add the tine, perchloride ; b must now be added very gradually to 

 a, the mixture being well shaken after each addition of the iron 

 solution ; keep this fluid in a stoppered bottle, and shake it well 

 before using it. This will form a transparent injection. (Beale.) 



TurnbuU's Blue. — 10 grains of pure sulphate of iron are to be 

 dissolved in an ounce of glycerine, or better still, in a little 

 distilled water, and then mixed with glycerine, and 32 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 the mixture ensured by 

 frequent agitation. The deep blue fluid thus prepared must be 

 added to i ounce of glycerine, i ounce of methylated spirit, and 

 4 ounces of water, as in the Prussian blue fluid. Dr. Beale con- 

 siders these proportions very large, and gives the following, which 

 I have not myself found to answer well, the injection, especially 



