400 GENERAL MICROSCOPIC TECHNIQUE. 



mentioned. Blood-vessels should usually be washed out with 

 salt solution before being filled with the injection mass. Fluids 

 containing alcohol (e. g., celloidin) cannot be injected until 

 the vessels have been washed out first with salt solution and 

 then with absolute alcohol. In using the gelatin masses, the 

 body or organ to be injected should be kept at a temperature 

 of 38-40 C. Constant pressure can easily be obtained by 

 means of a pressure bottle connected with a vessel of water 

 which may be raised to any given height. 



Some of the more useful injection masses are the following : 



(1) Berlin-blue. Saturated aqueous solution of Berlin-blue. 

 This should be made with distilled water. It forms one of the 

 most generally useful fluids we have. 



(2) Berlin-blue Gelatin. A saturated aqueous solution of 

 Berlin-blue is added to a gelatin solution heated to 60 C., and 

 filtered through flannel. 



(3) Carmine gelatin (Ranvier) : 10 grammes of gelatin are 

 allowed to swell up in distilled water for from twelve to twenty- 

 four hours. After it has been squeezed out with the hands 

 the gelatin is melted in a. water-bath (60 C.) and a carmine 

 solution added. The latter is prepared by mixing 5 grains 

 of carmine with 10 cc. of water, and adding drop by drop a 

 solution of ammonia until the fluid is a dark cherry red. A 

 solution of 30 per cent, acetic acid is then added carefully 

 until the mixture is exactly neutral, If it is at all alkaline, 

 the fluid will extravasate from the vessels. If, on the other 

 hand, it is acid, granules will be present, which will interfere 

 with its free passage through the capillaries. This is not an easy 

 fluid to prepare. It is possible to titrate the ammonia and acetic 

 acid, and, after thoroughly washing the gelatin to free it from 

 acid, corresponding quantities of the two solutions can be 

 added. 



(4) Lampblack gelatin, cinnabar gelatin, ultramarine-blue 

 gelatin, etc., can be prepared by adding the pigment granules 

 to a gelatin solution. Lampblack should be freed from the 

 fat which usually accompanies it. 



(5) Celloidin injection masses are made with a solution of 



