INJECTING BLOOD-VESSELS AND GLAND-TUBES. 89 



The turntable should be heavy and mounted on a pin-point 

 centre-piece. The brushes must not be too large, and should be 

 washed immediately after use in the same fluid as is used to dis- 

 solve the cement. Thus, for zinc-white the brush is to be washed 

 in benzol or xylol, and for gold-size in turpentine, and for Farrant's 

 solution in water. 



White Zinc Cement. Dissolve 3 oz. of dammar in 3 oz. of 

 benzol, and add 200 grains of finely-ground oxide of zinc. Mix the 

 whole thoroughly, and strain through several folds of muslin. It is 

 perhaps more convenient to purchase the cement. 



Mounting Block. It is important that the section be placed 

 in the centre of the slide. As a guide for this purpose, cut a 

 piece of paper the size of the slide, and draw diagonal lines from 

 corner to corner of it ; they will intersect in the centre. Or the 

 piece of paper may be gummed by means of Hollis's glue between 

 two slides. 



XV. INJECTING BLOOD-VESSELS AND 

 GLAND-TUBES. 



Transparent Injection Masses. At the present time, histologists 

 use transparent injections, consisting of a vehicle which may be 

 water, glycerine, or gelatine and a colouring matter. Most 

 commonly gelatine is used as a vehicle. The colouring matter of 

 most red injections is carmine. In this case, the secret is to have 

 the mass as neutral as possible. 



1. Carter's Carmine Injection. 



Carmine 



Strong solution of ammonia 



Glacial acetic acid 



Solution of gelatine (i to 6 water) 



Distilled water 



1 dr. 



2 fl. drs. 

 86 mins. 



2 oz. 



it,. 



Rub up the carmine with a little water in a mortar, add the 

 remainder of the water, and then add the ammonia, and stir until 

 the carmine is dissolved. Add the glacial acetic drop by drop, 

 stirring thoroughly. Add the gelatine solution, and stir briskly. 



2. Ranvier's Method. The following method yields excellent 

 results. Mix 2-5 grms. of pure carmine with a little distilled 

 water in a stoppered bottle, and add ammonia solution, drop by 

 drop, until the carmine, is dissolved, which occurs when the liquid 

 becomes transparent. Shake up the liquid to get it homogeneous. 



Weigh 5 grms. of dry Paris gelatine (Coignet's), and place it in 

 distilled water for one hour. At the end of this time it is swollen 

 up and soft. Remove it from the water, wash it in water, and 



