1884. | Microscopy. 219 
The “ fixation” of the animals in an expanded life-like form 
is perfect, and the action of the dilute acid is of so short 
duration that it causes no injury to the tissues. Not only infu- 
soria and rhizopods, but also large pelagic animals, such as Me- 
duse, Ctenophore, Salpæ, Heteropods, Doliolum, &c., may be 
thus killed and transferred to alcohol, with their form, histologi- 
cal structure, and cilia perfectly preserved. After complete re- 
moval of the yellowish color due to the presence of ferric salts by 
washing in acidulated alcohol, the tissues of transparent animals 
remain almost free from cloudiness, 
he best method of staining such objects is to add a few drops 
of gallic acid (one per cent solution) to the alcohol. After 
twenty-four hours the acidulated alcohol is turned off and pure 
alcohol added. Thus treated the protoplasm will take a light 
brown color, the nuclei a much deeper brown. Carmine stains 
too deeply and diffusely, and cannot be successfully removed. 
THE Preparation or Dry InjecTION-MASSES—The variously 
colored gelatine emulsions in common use as injections, keep for 
only a short time, and have therefore to be prepared as occasion 
arises for their use. The dry emulsions recommended by Fol are 
very easily prepared and convenient in use. As they will keep 
for any length of time, they can be prepared in quantities, and 
thus be ready for use at any moment. j 
, Carmine Emulsion —One kilogram gelatine (softer kind used 
in photography), soaked in water for a few hours until thoroughly 
Softened ; after turning off the water, heat the gelatine over a 
water bath until liquified; and then add to it, little by little, one 
liter of a strong solution of carmine in ammonia. The mixture 
stiffened by cooling is cut up, and the pieces packed in a fine 
Ee of netting. Vigorous pressure with the hand under water 
rces the emulsion through the net in the form of fine strings or 
vermicelli. These strings are placed in a sieve and washed until 
they are free from acid or excess of ammonia ; then collected and 
re-dissolved by heating. The liquid is poured upon large sheets 
aay ment which have been saturated with paraffine, and these 
of th are then hung up to dry in an airy place. The dried layers 
th © emulsion, which are easily separated from the parchment, 
ace be cut into strips and placed where they are protected from 
and dampness. 
pine Carmine solution used in this emulsion is prepared as fol- 
ma iig solution of ammonia is diluted with 3-4 volumes of 
is mj. and Carmine added in excess. After filtering, the solution 
change t With the gelatine, and then enough acetic acid added to 
comple the dark purple-red into blood-red. It is not necessary to 
n neutralize the ammonia. 
minutes "y emulsion requires only to be placed in water for a few 
and melted over the water-bath, to be ready for use. 
