44 The Microscope. 



When ready to make sections, remove the object and place upon 

 a cork which will tightly fit the well, or jaws of the microtome, first 

 placing a drop of the thicker solution of celloidin upon the cork 

 previously moistened with a drop or two of absolute alcohol. If 

 sufficient celloidin does not adhere to the object, flow a drop or so 

 over the object upon the cork. Leave it exposed to the air, under a 

 bell-glass until the surface begins to harden slightly. Then invert 

 the cork in a glass tumbler, containing a sufiicient depth of 00 to 90 

 per cent, alcohol; cover, and leave there for 12 to 24 hours, for the 

 celloidin and object to harden. It is now ready for sectioning. 

 Trim off surplus celloidin, put cork into microtome, and cut sections, 

 placing them, as cut, in dilute alcohol of C^0 to 90 per cent., where 

 they can remain till ready for staining, etc. If the object has not 

 been stained en masse, the sections may be stained in borax carmine, 

 using acid alcohol, in the usual manner, or they may be stained in 

 picrocarmine ; neither of these stain the celloidin to any great 

 extent. 



The sections may be prepared for mounting in balsam by pass- 

 ing through 96 to 98 per cent, alcohol, or by j^assing through car- 

 bolic acid. I generally use the latter. The sections may be trans- 

 ferred direct from 60 per cent, alcohol into the acid and will clear up 

 beautifully in a few moments, and but few objects are injured or 

 changed by the acid in that time. The sections may then be 

 mounted immediately in balsam, first draining off as much as possi- 

 ble of the acid. Where acid can not be used, without injuiy, dehy- 

 drate with alcohol, not absolute, for that will dissolve the celloidin, 

 but with that of about 96 per cent., and then mount in balsam, or 

 which is often better, mount in glycerine, without dehydrating. If 

 glycerine is used for mounting, it is necessary that the object be pre- 

 pared in the usual manner by first soaking in various strengths of 

 that material. 



Absolute alcohol, ether and clove oil dissolve celloidin. Oil of 

 bergamot may be used to clear sections after dehydrating as above. 



I have preparations of insects, chrysalids, plant ovaries, com- 

 posite and other flowers, and of the human fcetus, prepared in the 

 manner indicated above, in which every organ and part is displayed 

 in situ; in a preparation of the thorax of the human foetus, about 

 three months old, the lungs, liver, heart, spinal cord and all other 

 parts are beautifully displayed. 



It is also very valuable in preparations of the mosses, plant 

 hairs, plant glands and of all delicate appendages, where it is desired 

 to section them and retain eveiy part in place. 



