102 THE MICROSCOPE 



body else wrong, but I hope I would not do so against good evi- 

 dence to the contrary. 



^be niMcroecopc anb bow to use it 



By V. A. Latham, F.M.S. 



Part X. — Injecting {continued). 

 Plate XIV. 



The Dry Injection Emulsions are easily prepared and conven- 

 ient in use. As they will keep for any length of time, they can 

 be prepared in large quantities, and thus be ready for use at any 

 moment. 



Carmine Injection Emulsion. — Soak i kilogram of gelatine 

 (the softer kind used in photography) in water for a few hours until 

 thoroughly softened ; drain off the water, heat the gelatine over a 

 water bath until liquified ; then add, drop by drop, i litre of 

 strong carmine in ammonia. The mixture, stiffened by cooling, 

 is cut up, and pieces packed in a fine piece of netting. Vigorous 

 pressure with the hand under water forces the emulsion through 

 the net in the form of fine strings. These are placed in a sieve, 

 and washed until free from acid or excess of ammonia ; collect 

 and redissolve by heating. Pour the liquid then on large sheets 

 of parchment which have been saturated with paraffin, and then 

 hang these sheets up to dry in an airy place. The dried layers of 

 the emulsion are easily separated from the parchment, when they 

 should be cut into strips and placed where they are protected 

 from dust and dampness. The carmine solution used in this 

 emulsion is made as follows : — A strong solution of ammonia is 

 diluted with from three to four volumes of water, and carmine 

 added in excess. After filtering, the solution is mixed with the 

 gelatine, and then enough acetic acid added to change the dark 

 purple-red into blood colour. It is not necessary to completely 

 neutralise the ammonia. The dry emulsion requires only to be 

 placed in water for a few minutes and melted over a bath to be 

 ready for use. 



J 



