CHAPTER X 

 CELLOIDIN* AND OTHER IMBEDDING METHODS 



181. Introduction. Celloidin, Parlodion and Photoxylin are the 

 chief commercial preparations of nitrocelUilose which have been 

 used for imbedding since Duval {Journ. de VAnat., 1879, p. 185) 

 introduced his collodion method. In comparison with paraffin 

 wax imbedding, the celloidin techniques possess several important 

 advantages. The shrinkage and distortion, so common in paraffin 

 sections and particularly in the case of large blocks of material, 

 is minimised. Celloidin tends so often to be used only for tough 

 or brittle tissues and it should be stressed that the minute details 

 in the morphology and staining reactions of various cell-types, 

 such as occur in hsemopoietic tissues, are more completely preserved 

 in celloidin sections. The student should examine celloidin sections 

 of lymph glands, for instance, and note the preservation of the 

 lymphocytes which undergo marked shrinkage during paraffin 

 imbedding. Owing to the elastic nature of celloidin, loose mem- 

 branes and fragile or brittle areas in tissues are more easily kept 

 intact in the sections. For this reason celloidin imbedding is 

 invaluable for nervous tissues which have been made brittle by 

 prolonged mordanting. It is not necessary, of course, to remove 

 the transparent celloidin before mounting the sections. A few 

 special tissues like tendon, fibrocartilage, nails and claws, together 

 with the invertebrate forms possessing chitinous or horny parts, 

 are seldom sectioned successfully without the use of celloidin. 

 Much of the characteristic hardness of these special tissues, 

 following paraffin imbedding, is due to the action of hot wax and 

 can be avoided with the celloidin technique. Material cut in 

 celloidin usually has a greater affinity for dyes as compared with 

 paraffin sections. Whereas the majority of the routine staining 

 techniques in this textbook are generally used with paraffin 

 sections, a few, e.g. Mallory's triple connective tissue stain, were 

 originally devised for celloidin sections and undoubtedly give more 

 specific reactions in celloidin. Celloidin imbedding is essentially 

 a technique for the critical histologist and embryologist who is 

 concerned with these advantages and not with the main 

 disadvantage of the time taken in preparing the sections. 



182. Resume of Celloidin Imbedding Techniques. The process 

 of celloidin imbedding is open to more variations than paraffin wax 



* K. C. R. 



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