54 THE MICROSCOPIC PREPARATION. 



masses. The vehicle of the latter is most generally gelatin. For inject- 

 ing the blood-vessels either the cold or the warm masses may be employed, 

 although the latter gives better results. The cold masses are to be used 

 for injecting the lymphatic vessels. In injecting the blood-vessels it is 

 well to wash out the vessels with warm normal salt solution before the in- 

 jection mass is forced into the vessels. The following masses may be 

 recommended : 



Gelatin=carmin. The first is a gelatin -carmin mass, and is 

 prepared as follows: (i) 4 gm. of carmin are stirred into 8 c.c. of 

 water and thoroughly ground. Into this a sufficient quantity of ammonia 

 is poured to produce a dark cherry color and render the whole transpar- 

 ent. (2) 50 gm. of finest quality gelatin is placed in distilled water for 

 twelve hours until well soaked. It is then pressed out by hand and 

 melted at a temperature of 70 C. in a porcelain evaporating dish. The 

 two solutions are now slowly mixed, the whole being constantly stirred 

 until a complete and homogeneous mixture is obtained. To this mass is 

 added, drop by drop, a 25% acetic acid solution until the color begins 

 to change to a brick red and the mass becomes slightly opaque. This 

 should be very carefully done, as a single drop too much may spoil the 

 whole. During this procedure the substance should be kept at 70 C. 

 and constantly stirred. The change in color indicates that the reaction 

 of the mass has become neutral or even slightly acid (an ammoniac solu- 

 tion should not be used, since the stain diffuses through the wall of the 

 vessel and colors the surrounding tissues); the whole is filtered through 

 flannel while still warm. As this mass hardens on cooling it is injected 

 warm. The instruments used are also warmed before the injection is 

 begun. 



Gelatin-Berlin Blue. One part of oxalic acid is powdered in a 

 mortar; to this is added one part of Berlin blue and 12 parts of water. 

 Stir and rub until a solution is obtained. Prepare a gelatin vehicle as 

 directed in the preceding paragraph ; to 1 2 parts of the gelatin mass add 

 slowly while stirring 12 parts of the Berlin blue solution. The whole is 

 filtered through flannel while still warm. 



Yellow Gelatin Mass (Hoyer). Prepare a gelatin vehicle consist- 

 ing of i part of gelatin and 4 parts of distilled water ; a cold, saturated 

 solution of bichromate of potassium and a cold, saturated solution of lead 

 acetate. Take equal volumes of each. Add the bichromate of potassium 

 solution to the gelatin and heat almost to boiling; then add slowly, 

 while stirring, the lead acetate solution. 



Carmin Mass, Cold (Kollmann). One gm. of carmin is dissolved 

 in a small quantity of ammonium hydrate and 20 c.c. of glycerin added. 

 To another 20 c.c. of glycerin there is added 20 drops of hydrochloric acid 

 and this added to the glycerin -carmin mixture while stirring. 



Saturated aqueous solutions of Berlin blue or a Prussian blue may also 

 be used for cold injections. 



Injection masses already prepared are to be had in commerce. 

 Besides those already mentioned, still others colored with China ink, etc., 

 are in general use. 



Small animals are injected as a whole by passing the cannula of 

 a syringe into the left ventricle or aorta. In the case of large animals, 

 or where very delicate injections are to be made, the cannula is inserted 

 into one of the vessels of the respective organs. The proper ligation of 

 the remaining vessels should not be omitted. 



