1899] MICROSCOPICAL JOURNAL 213 



better still, 70 per cent alcohol, and, with a pair of 

 tweezers, gently lower the paper thimble, or mould — For 

 such it is — into the alcohol. Leave it until the celloidin 

 has turned milky white, and, in point of fact, returned to 

 the original consistency of the cake celloidin. The ob- 

 ject of doing this is to prevent the specimen when put 

 into the mould from touching the wood, and so enabling 

 the operator to cut sections down to the uttermost layer, 

 which would obviously be impossible if it rested on the 

 bottom. If the wood had not been previously soaked in 

 solution, multitudes of bubbles would rise when submit- 

 ted to the action of the spirit, and become imprisoned in 

 the congealed mass, rendering it spongy and yielding to 

 the knife. Now remove the mould from the spirits, dry 

 off the alcohol, put a drop or two of thin celloidin on the 

 floor of the cylinder, lay the specimen carefully thereon, 

 seeing that it stands isolated, and pour enough thick so- 

 lution over to well cover it. At this stage, provided the 

 whole is of a good stiff consistency, I have transferred it 

 at once to rectified spirits; but in every case the precau- 

 tion must be taken of exposing it beforehand to the air 

 for a short time — half an hour is not too long, so as to al- 

 low a skin to form, which will prevent the alcohol acting 

 too rapidly and breaking up the mass. The celloidin be- 

 comes more and more opaque, finally, iu the course of an 

 hour, turning white and waxy, when the paper may be 

 easily peeled off, and the whole, with the wooden disc at- 

 tached, and which must on no account be detached, can 

 then be kept indefinitely in spirits until required for cut- 

 ting. Bolles Lee recommends that the imbedded object 

 be kept for some days under a tight-fitting bell-jar, al- 

 lowing fresh air to have accsss daily, before transferring 

 to the alcohol bath, but I have never found it necessary. 

 Other methods have been recommended for hardening the 

 mass, upon the successful issue of which the after cutting 

 largely depends — chloroform, for example, which not only 



