CHAPTER IX. 



COLLODION (CELLOIDIN) AND OTHER IMBEDDING METHODS. 



156. Introduction. Collodion (or celloidin) masses do not 

 require the employment of heat. They do not require that 

 the objects should be cleared before imbedding, and that is 

 an advantage in the case of very large objects. They are 

 more or less transparent, which facilitates orientation. And 

 they are specially indicated for very large objects, for the 

 soaking in collodion, being quite inoffensive to the most 

 delicate elements, may be prolonged if necessary for weeks. 

 Lastly, the mass being quite transparent after mounting, it 

 is not necessary to remove it from the sections before staining 

 and mounting them ; it may remain, and fulfil the function of 

 an admirable support to the tissues, holding in their places 

 brittle or detached elements that without that help would 

 fall to pieces and be lost. 



There are disadvantages. One is that the process is a 

 very long one ; as usually practised, it requires some three 

 days for the imbedding of an object that can be imbedded 

 in paraffin in an hour. Another is that it is impossible to 

 obtain with celloidin sections quite so thin as those furnished 

 by paraffin. 



In the older celloidin method the mass is cut wet, "before, 

 clearing. I strongly recommend the more recently intro- 

 duced practice of clearing before cutting, and cutting dry as 

 described in 168-170. 



157. Collodion, Celloidin, and Photoxylin. The collodion 

 method is due to DUVAL (Journ. de VAnat., 1879, p. 185). 



Celloidin, recommended later on by MERKEL and SCHIEFFER- 

 DECKER (Arch. Annf. Plujs., 1882, p. 200), is merely a patent 

 collodion. It may be obtained from GRUBLER, or the other 

 dealers in histological reagents. It is sent out in the form 

 of tablets. These tablets may, if desired, be dissolved at 



