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 a 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. 



