ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 429 



specimens for a longer time — then transfer it to a mixtm-e of tur- 

 pentine and paraffin, kept melted on a water-bath, at about 40^ C. In* 

 this the specimen, if from liver or intestine, &c., should remain for an 

 hour or more ; small nerves and blood-vessels of course need not 

 remain so long. Then transfer it to a bath of pure paraffin, melted 

 at a temperature of 60° C, and leave it for the same length of time. 

 Indeed, if care be taken that the temperature does not materially 

 exceed 60°, the specimen may remain as long as convenient. When 

 the tissue is thoroughly saturated with melted paraffin, a small 

 paper box may be filled with melted paraffin and the specimen 

 placed in it to cool. If properly imbedded, a cut surface has a 

 smooth and shining appearance. No line of division must appear 

 between the specimen and surrounding paraffin. The whole mass 

 should cut, as nearly as possible, like one homogeneous mass of 

 paraffin. 



The subsequent handling of the sections varies with theii' nature. 

 Moderately thick sections of firm tissue may be placed in turpentine 

 to remove the paraffin and mounted as usual in chloroform-balsam. 

 Thin specimens, or those which come to pieces when the paraffin 

 is removed, like thin sections of liver, &c., may be laid on the slide 

 on which they are to be mounted, and the paraffin washed out by 

 benzine, carefully applied by a dropping-tube ; allow the benzine to 

 evaporate, then lay on the cover-glass and apply thin chloroform- 

 balsam at the edge of the cover. For exceedingly delicate specimens, 

 such as embryos or osmic acid nerves, another method may be used. 

 Lay the section on the slide, wet -ndth absolute alcohol, and let the 

 alcohol completely evaporate, leaving the specimen attached to the 

 slide ; carefully heat until the paraffin is softened or slightly 

 melted. When cool, let a few drops of benzine — best applied with a 

 brush — run over the section until most of the paraffin 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. The 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 

 vertebrate soft tissues, chick and trout embryos, hydras, snails, 

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

 case. The ease with which the sections can be made fully com- 

 pensates for the time required to imbed. 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 ^^ °^^- tliick in one day, and mounted 

 them without losing any sections. No one who practises with 

 these specimens will regard this as much of a feat ; it is simply a 



