CELLOIDIN IMBEDDING 503 



to flatten them on water. They may be laid down on Mayer's 

 albumen, without water, gently pressed down with a brush, and the 

 paraffin melted and dissolved at once, the whole process taking only a 

 few seconds. But for delicate histological work it is well to employ 

 the water method in any case, as the flattening on water serves to 

 somewhat expand the sections, which, unless cut from extremely 

 hard paraffin, are generally somewhat compressed by the impact of 

 the knife. 



As soon as the paraffin has been removed, all that is necessary, 

 in the pure water process, is to add a drop of balsam and a cover, if 

 the material has been already stained. If not. the solvent of the 

 paraffin is removed by alcohol, ai^d the sections are stained in any 

 manner that may be desired. 



But if Mayer's albumen has been employed the sections must be 

 thoroughly washed with alcohol before the definitive clearing and 

 mounting. This is necessary in order to remove the glycerin, which 

 would otherwise cause turbidity in the mount. 



Tubes for Handling Serial Sections. The most convenient 

 vessels for performing the various operations of washing, dehydrating, 

 clearing, staining, &c., with sections fixed to the slide, are flat 

 bottomed corked tubes. They should have an internal diameter 

 slightly over 1 inch, so as to be able to take two slides placed back 

 to back ; and they should be nearly 4 inches high, so as not only 

 to take the slides in an upright position, but to allow room for the 

 cork. A stand is easily made for them by taking a piece of inch 

 deal board, and boring in it with a centrebit holes about ^ inch 

 deep, large enough to take the bottoms of the tubes, and about 1 inch 

 apart. A board with three rows of seven holes each does not take 

 up too much room on the work-table. 



The Collodion or Celloidin Imbedding Method. Celloidin is a 

 patent collodion, sent out in semi-dry tablets. It may be obtained 

 through Griibler and Hollborn. To prepare it for use for imbedding 

 it may either be dissolved at once in a mixture of equal parts of 

 ether and absolute alcohol, or, which is held by some workers to be 

 preferable, it may be cut up into thin shavings, which are allowed to 

 dry in the air until they have assumed a horny consistency, and are 

 then dissolved in the ether and alcohol. It is held that by thus 

 drying the celloidin all water is removed from it, and a more favour- 

 able imbedding mass obtained. Either celloidin or common collodion 

 may be used for imbedding, celloidin having merely the advantage 

 stated. 



A thin celloidin solution is made by dissolving from 4 to 

 6 per cent, of the dried shavings in the alcohol and ether mixture ; 

 a thick one by dissolving from 10 to 12 per cent, of them. 

 Thicker solutions than this are not necessary. If common collodion 

 be taken, a thin solution should be prepared by diluting it with 

 ether. 



The objects to be imbedded must first be thoroughly dehydrated 

 with absolute alcohol. They are then soaked, till thoroughly pene- 

 trated, in ether, 01% which is better, in a mixture of ether and 

 absolute alcohol. They are then brought into the collodion. 



