182 PREPARATION AND MOUNTING 
the force required grows greater, yet care must be taken not 
to use too much, or the vessels will burst, and render all the 
labour fruitless. The movement of the piston must be 
occasionally so slow as to be almost imperceptible, and for 
this reason the piston-rod is sometimes marked with lines 
about one-eighth of an inch apart. 
19. Of course, during the whole process the injecting 
fluid and subject must be kept at a temperature high enough 
to allow the liquid to flow freely ; and the escape of a little 
of it need cause no fears to the operator, as it is almost im- 
possible to fill a subject without some loss. When the 
injected object has received sufficient fluid, it should have a 
plump appearance, owing to all the vessels being well filled. 
The vessel must then be tied up where the pipe was inserted, 
and the whole left in cold water two or three hours, after 
which time it may be mounted ; but it may be well to notice 
a few things which the beginner ought to know before enter- 
ing into that part of the process; and he may be here informed 
that it is not necessary to mount the objects immediately, 
otherwise it would be impossible for one person to make 
ase of half of any large subject, as it would be in a state 
of decay long before each part could have been examined 
and separated. Large pieces should be therefore immersed 
in equal parts of spirits of wine and water, or glycerine, 
which some think better still, and thus preserved in bottles 
until time can be given to a closer examination. 
20. In operating upon large subjects, entire animals, &c., 
the constant pressure required by the piston of the syringe 
srows wearisome, besides occupying both hands, which is 
sometimes inconvenient when working without assistance. 
To obviate this, another way of driving the syringe was 
published in the Micrographic Dictionary which I will 
quote here :—‘ We have therefore contrived a very simple 
piece of apparatus, which any one can prepare for himself, 
and which effects the object by mechanical means. It con- 
sists of a rectangular piece of board, two feet long and ten 
inches wide, to one end of which is fastened an inclined 
