OF MICROSCOPIC OBJECTS. 183 
piece of wood (equal in width to the long board, and one 
foot high). The inclined portion is pierced with three holes, 
one above the other, into either of which the syringe may 
be placed—the uppermost being used for the larger, the 
lowermost for the smaller syringe; and these holes are of 
such size as freely to admit the syringe covered with flannel, 
but not to allow the rings to pass through them. The 
lower part of the syringe is supported upon a semiannular 
piece of wood, fastened to the upper end of an upright rod, 
which slides in a hollow cylinder fixed at its base to a small 
rectangular piece of wood; and by means of a horizontal 
wooden screw, the rod may be made to support the syringe 
at any height required. The handle of the syringe is let 
into 4 groove in a stout wooden rod connected by means of 
two catgut strings with a smaller rod, to the middle of 
which is fastened a string playing over a pulley, and at the 
end of which is a hook for supporting weights, the catgut 
strings passing through a longitudinal slit in the inclined 
piece of wood.” When in use the syringe is filled with 
injecting fluid, and passed through one of the three holes 
which is most suitable. The object being placed so that the 
pipe and syringe can be best joined, the rod and strings are 
’ set in order, and a weight placed on the hook. The stop- 
cock must then be opened gradually, when the operator 
will be able to judge whether the weight is a proper one or 
not: if the piston is driven with any speed, there is danger 
of injuring the subject, and less weight may be used; if, 
however, the piston do not move, more must be added.* 
21. Such is the method recommended in the Micro- 
graphic Dictionary, and perhaps it is as good as any 
mechanical plan could be; but where the operator is willing 
to undergo the labour of performing all this with the hand, 
he has a much better chance of succeeding, because the 
pressure can be regulated so accurately, and changed so 
* There is in the Monthly Microscopic Journal, vol. ii., page 48, 
another ingenious apparatus for injecting purposes. 
