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 veryjong. 

 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 introduced practice of 

 clearing before cutting, and cutting dry as described in 168170. 



157. Collodion, Celloidin, Parlodion 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. Anat. Phys., 1882, p. 200), is merely a patent collo- 

 dion. ' It may be obtained from almost all of the usual dealers in 

 histological reagents. It is sent out in the form of tablets. These 

 tablets may, if desired, be dissolved at once in ether, or a mixture 

 of ether and alcohol, to make a collodion of any desired strength. 

 But it is better, as recommended by APATHY, to cut them up into thin 

 shavings, which should be allowed to dry in the air until they become 

 yellow, transparent, and of a horny consistency, and that these be 

 then dissolved in alcohol and ether (sulphuric, free from acid). 

 The solutions thus prepared are free from the excess of water that is 

 present in the undried celloidin, and give after hardening a mass 



