180 THE AMERICAN MONTHLY [June, 



paraffin sections are cut dry while the celloidin must be 

 cut under, or flooded with weak alcohol. Harden and 

 dehydrate the tissue in absolute alcohol, then keep it in 

 thin celloidin solution for 24 hours, (15 grains of Sher- 

 ing's celloidin dissolved in 100 cc. of equal parts of ab- 

 solute alcohol and ether). Then transfer to a thick so- 

 lution which should be made containing enough celloi- 

 din to secure the consistence of a thick syrup. Let it 

 remain in this solution from 24 to 48 hours. 



Fasten the tissue, by the thick solution, to a cork or 

 better, a small block of wood ; (care being taken that a 

 stratum of celloidin lies between the tissue and the cork 

 or wood) and a number of layers of celloidin should be 

 placed around the tissue. In a few minutes the celloi- 

 din will be hardened by the evaporation of alcohol and 

 ether, and it is ready to cut. 



As it has been mentioned above, the celloidin sections 

 are cut under a stream or flooded with weak alcohol 

 (50 to 70 per cent). These sections can now be stained 

 and dehydrated in 95 per cent alcohol and cleared in xy- 

 lol, oil of bergamot or cedar oil. In either method the 

 tissue can be stained before dehydration and imbedding. 

 In some cases staining in mass is preferable to staining 

 in sections. 



In reading over the two methods, one will notice the 

 simplicity of the latter process. It is an excellent method, 

 especially adapted for certain lines of work in the cen- 

 tral nervous system and special senses, and possesses the 

 advantages over paraffin of requiring less attention, and 

 no heat for its successful manipulation. It gives suflB- 

 cient support to the tissue, and its transparancy {verre 

 elastique nenut sie Duval), does not interfere with the 

 topography of the field. 



But in using this method, the sections are thicker than 

 those of the paraffin and it is not applicable for serial 



