318 JOHN BERRY HAYCRAFT, 
figure of a muscular fibre on a small scale, and it shall be made 
out of a substance of uniform consistence throughout. What 
appearances shall we see on microscopic examination? This has 
been accomplished in the following manner: A glass rod is 
Fic. 4.—This shows the passage. The convex parts converge the rays to 
focus 4’ A” al”, after which they diverge. The lens shifted up or 
down (vertically) over the ridges, and depressions will focus on the 
retina alternately, converging and diverging rays. 
heated in a spirit-lamp and plunged into a bottle of Canada 
balsam ; it is then withdrawn, and a little drop of the balsam is 
allowed to fall on a glass slide, or a thread of it may be laid out 
on the surface of the glass. Before the drop or thread has 
solidified it is indented with the milled head of a fine screw, 
