Chapter VII: The Celloidin Method 63 



which is a mixture of equal parts of bergamot oil, cedar oil, and anhy- 

 drous carbolic acid. 



5. Imbedding a Number of Objects in one mass is frequently conven- 

 ient. Fold a stiff paper into a box of the proper size (chap, v, step 6) 

 or use metal Ls (Fig. 30). Pour in thick celloidin, put the objects in 

 place and orient them properly for cutting. Leave a space of about 

 8 mm. between adjacent objects. Fill the box with thick celloidin and 

 set it in a dish containing a little chloroform, or leave it in 80 per cent, 

 alcohol to harden. When ready to proceed, cut the large blocks into 

 smaller ones each containing a piece of tissue. To fasten it to the wood, 

 trim the small celloidin block to the proper dimensions, soften for a few 

 minutes in ether-alcohol, the side to be attached, then dip it into thick 

 celloidin and apply to the end of a wooden block which likewise has been 

 dipped into the ether-alcohol and the thick celloidin. Press the two 

 together and place them in chloroform or 80 per cent, alcohol to harden. 



6. Anilin Dyes are usually avoided in the celloidin method because 

 they stain the celloidin intensely and are not removed in subsequent 

 treatment. When necessary, however, some (e. g., eosin) may be used. 

 Saffranin, for example, may be removed satisfactorily from the celloidin 

 by means of acid alcohol without extracting all the stain from the tissue. 

 If anilin dyes have been used it is sometimes better to remove the celloi- 

 din by treating the sections with absolute alcohol or with ether before 

 the final clearing and mounting. 



7. Relative Merits of the Paraffin and the Celloidin Methods. Celloidin is 

 good for large objects, for brittle or friable objects, and for delicate objects 

 which heat would injure. It does not require removal from the tissues 

 ordinarily, hence it holds delicate structures together permanently. 

 Very thin sections cannot be cut, consequently it is of little value in 

 cytological work. It is usually impractical to attempt to cut sections 

 under 10 microns in thickness. The method, moreover, is extremely 

 slow. The paraffin method is comparatively rapid, serial sections may 

 be cut and mounted with ease, and very thin sections may be obtained. 

 Large objects do not section satisfactorily, although up to 10 mm. or 

 even greater diameter they cut readily. The rule is to use the paraffin 

 method when you can. 



8. For Brittle Objects, a Combination of Celloidin and Paraffin Infiltration 

 sometimes proves successful. The method is too tedious for ordinary 

 use although it must sometimes be resorted to with friable or delicate 

 objects such as eggs. Infiltrate with celloidin in the usual manner 

 and imbed in a paper box, but do not mount on a block. Harden 

 in 80 per cent, alcohol, transfer to 95 per cent, alcohol for 12 hours, 

 immerse in pure origanum oil and 95 per cent, alcohol equal parts for 12 

 hours, then in pure origanum oil for 2 to 3 hours; next transfer to a mix- 



