56 THE MICROSCOPE. 



ply thin chloroform-balsam at the edge of the cover. For exceed- 

 ingly delicate specimens, such as embryos or osmic acid nerves, an- 

 other method may be used. Lay the section on the slide, wet with 

 absolute alcohol, let it completely evaporate, leaving the specimen 

 attached to the slide; carefully heat until the paraffine is softened, 

 or slightly melted. When cool, let a few drops of benzine — best 

 applied with a brush — run over a section until most of the paraffine 

 is gone. When dry, apply the cover-glass and put a thin solution of 

 Canada-balsam in xylol to its edge. The xylol may be used instead 

 of benzine but it is more expensive. 



This method is very convenient, especially for histological 

 laboratories. I'he specimen once imbedded, can be kept for years< 

 and new sections cut as wanted. No change takes place in it nor 

 can it dry up. It is suited to all tissues. I have imbedded all 

 vertebrated soft tissues, chick and trout-embryos, hydras, snails, 

 angle worms, clams, star- fishes, etc., with equal success in every 

 case. 



The ease with which the sections can be made, fully compen- 

 sates for the time required to embed. The merest tyro, provided 

 with a good section-cutter, a brush to keep the sections from rolling, 

 and such a specimen, must be a bungler indeed if he cannot cut at 

 least thirty even sections from each millimetre of a moderate-sized 

 specimen such as the oesophagus of a rabbit. With a little practice 

 he should be able to cut a millimetre into one hundred sections 

 without losing more than two. The writer has cut a frog's spinal 

 cord so imbedded into 926 sections -^^ m.m. thick in one day, and 

 mounted them v/ithout losing any sections. No one who practices 

 with these specimens will regard this as much of a feat. It is simply 

 a hard day's work. 



Specimens as large as the central hemisphere of a rabbit can be 

 stained and imbedded whole. 



I append my notes on the spinal cord of a frog, showing the 

 times used in the various processes: — 



Cord put into 3 per cent, nitric acid, two hours. 

 Seventy per cent, alcohol, six hours. 

 Stained in hcematoxylin, four hours. 

 Seventy per cent, alcohol, over night. 

 Ninety-five per cent, alcohol, twenty-four hours. 



