*Jouma\ST?8^^^^^^^ NOTES AND MExMORANDA. 219 
plan of a movable tool. A little consideration will, however, show 
that to keep the point worked with in view it must be perfectly steady 
in the field of the objective, and, further, that in the stage and body 
movements of the modern microscope we have a most perfect appa- 
ratus for executing any kind of work by substituting motion of the 
object for that of the tool. This principle once adopted, it becomes 
comparatively easy to adapt instruments to the kind of work required, 
and I append descriptions of those I have myself employed, less that 
I regard them as the best practicable arrangement, than that, being 
easily constructed by any one at the cost of a few pence, they serve as 
a ready means of ascertaining the practical value of the system. 
To the arm, or any flat part of the microscope between the coarse 
and fine adjustments, attach a stiff, square plate of metal, about 
1^ inch diagonally, by two binding screws working through slits in 
opposite corners, so as to permit the plate a horizontal motion of 
about |th of an inch. To this plate is soldered vertically a stout 
steel spring clip, readily made as follows : — Procure one of Lund's 
patent paper clips, sold by most stationers ; heat it red hot, to destroy 
the temper ; then, with a stout pair of scissors, cut the slit to the 
width of about ^th of an inch, and retemper the tube. 
Select some glass tube of a size to slide rather stiffly in this clip, 
draw it out at one end to about ^th of an inch thickness, bend the 
thin part at an angle of 45°, and draw out so as to keep it at this 
thickness for half-an-inch, or rather more, and cut it off. Three or 
four of such tubes will be useful. Next take a common vaccine tube 
and draw it out in a spirit-lamp to the finest possible point. 
Place one of the prepared tubes in the clip, first attaching this to 
the microscope, and set it so that the angular part of the tube points 
as nearly as you can guess to the field of the objective you intend to 
use. Measure as accurately as you can the distance of this end from 
the centre of the field, and having found it, measure the same distance 
on the vaccine tube from the fine end. At the point thus found apply 
a little sealing-wax round the vaccine tube, and having moderately 
heated the thin end of the other tube, insert the vaccine tube into it, 
when it will quickly become fixed in any position desired. When the 
tube is replaced in the clip, the point of the vaccine tube should admit 
of being brought into the centre of the field of the objective used. If 
it should not do so, the sealing-wax may be reheated, and the vaccine 
tube shifted as required. Minor corrections may be made by the 
sliding motion of the clip-holder. 
You will thus have fixed in the field, and moving with it, a mani- 
pulator far more delicate and elastic than any needle or hair. How- 
ever, either needle or hair may be used in the same way if desired. 
For dissection a thick needle beaten while red hot to a spatula end, 
well retempered, and ground to a very fine edge, will be a good form 
of knife. 
It would be easy to adapt a forceps arrangement, if desired ; but 
for most purposes the syringe I am about to describe will be preferable. 
The body of the syringe is constructed exactly as the manipulator 
above described, except that the point of the vaccine tube is broken 
