ea 
THE MICROSCOPE. 21 
is not obtainable, the opaque, white interior of older lac will answer. 
This lac is poured over the slide forming a thin varnish on one side. 
It is usual to prepare a large number of these slides at once, placing 
a small label in one corner so as to indicate the varnished side and 
also the corner in which the series of sections begins. Sometimes 
difficulty will be experienced in making the coating of varnish 
transparent but this can readily be obviated by heating the slide 
slightly immediately before applying the varnish. 
Then the ribbons .of sections are placed in regular order 
on the slide after which the slide is exposed to a heat sufficient 
to melt the paraffin when the sections become affixed to the lac. 
After cooling, the paraffin is dissolved and washed away by benzole 
or turpentine; balsam is next placed on the sections and a cover 
glass placed in position and the slide finished in the usual manner. 
This method has the disadvantage that the object must be 
stained before cutting. A second method admits of staining after 
the sections are cut and arranged on the slide. Instead of the 
solution of lac a solution of india-rubber in benzole or chloroform 
is applied to the slide in the same manner. The subsequent treat- 
ment is the same until after the paraffin is dissolved by the turpen- 
tine. Next the turpentine is cleaned off by absolute alcohol and 
then the slide is immersed in any staining fluid desirable. The 
subsequent processes are those usually employed, dehydration by 
absolute alcohol,treatment by oil-of-clove and mounting in balsam 
or dammar. 
There are several minor details which add to the convenience 
of this method... It is desirable to employ larger slides than 
the regular three inches by one in usual use in this country. The 
cover glasses also should be larger, and square or rectangular ones 
are much preferred to round. In placing the sections on the slide 
it is most convenient to have the rows run first from left to right, 
next from right to left, etc., as shown in the diagram. 
r 2 3 4 5 
10 9 8 yi 6 
EL) ES) jy CAD aes 
20;7*, 809) | TO. pine 
This adds greatly to the convenience of examination as the sequence 
is more rapidly followed under the microscope. 
These processes are the combined results obtained by several 
students, the most prominent being Dr. Caldwell, of Cambridge, 
England, and Professor Giesbrecht, of Naples. These methods 
have been extensively tested both in this country and in Europe and 
- have been found eminently practical and I commend them from 
experience to all American students. 
J. S. Kincstey, iz Science Record. 
