TRICHINA SPIRALIS. 19 
Otherwise the instruments are similar in all respects, and therefore 
we shall confine our description to that shown in Figs. 6, 7 and 8. 
Here we have two metal plates hinged together at one end, and 
so arranged that they may be powerfully forced together by means 
of the screw at the other end. In the section, Fig. 7, a and b are the 
metal plates, out of the centre of which a large space has been cut, 
so as to permit the observer to look through the glass ,plates, c 
andd. The screw, s, serves to force the plates together, and the 
microscope, J, may be moved from end to end and also across the 
plates, so as to command a view of every part. The microscope is 
adjusted for focus by being screwed up or down in the socket at the 
end of the arm which carries it. 
When desired, a compound microscope may be used in connection 
with the plates, as shown in Fig. 9, instead of the doublet shown in 
Fig. 7. Our own preference is for a doublet. 
The method of using the instrument is very simple. A thin slice 
of flesh having been moistened with a mixture of equal parts of 
