CHAPTER X 



THE CELLOIDIN METHOD 



The celloidin method has almost disappeared from botanical micro- 

 technique, because material too hard for imbedding in paraffin can be 

 cut without any imbedding at all, and material too delicate to be cut 

 without a supporting medium can be imbedded in paraffin. But these 

 two categories do not cover all the ground; celloidin still has its ad- 

 vantages. Stems too hard for the paraffin method, which lose the 

 cortex or, at least, suffer breaks with the steam method or when cut 

 freehand and cold, can often be cut successfully in celloidin. 



Years ago, a piece of rotten wood from an ancient Egyptian mum- 

 my case was brought to the writer for identification. It could be rubbed 

 into powder in the fingers, and had to be handled gently to keep it 

 from falhng to pieces. It was cut very successfully in celloidin. Stems 

 too hard for paraffin may be cut in celloidin when it is desired to pre- 

 serve cell contents. Celloidin is still very valuable for most of the sec- 

 tions used in medical schools, because the sections can be prepared in 

 great numbers and each student can take a section, add a drop of bal- 

 sam and a cover, and have a preparation of his own ready to study. 

 Where serial sections are necessary, as in most morphological and cy- 

 tological work, the method is too tedious to be worth even a trial, un- 

 less the sections cannot be cut in any other way. Besides, most of the 

 more valuable stains color the celloidin matrix, and if the matrix be 

 removed, the more delicate elements may be displaced or even lost. 



Celloidin and collodion are forms of nitro-cellulose. They are in- 

 flammable, but do not explode. Schering's celloidin, which is only a 

 collodion prepared by a patented process, is in general use for imbed- 

 ding. Granulated and shredded forms of celloidin are on the market, 

 but the tablets are more convenient. Directions for making the vari- 

 ous solutions accompany the celloidin. To make a 2 per cent solution, 

 add to 1 tablet enough ether-alcohol to make the whole weigh 2,000 g. 

 To make a 4 per cent solution, add another tablet, and to make a 6 per 

 cent solution, add an additional tablet, and so on. 



The collodion method was pubhshed by DuvaP in 1879. Celloidin 



'Duval, Journal de Vanatomie, 1879, p. 185. 



132 



