GENERAL MICROSCOPY 



mold attack can be rendered very clearly- 

 visible with a phase contrast microscope. 



Even a fairly slight attack causes a loss in 

 double refractivity and therefore a polariza- 

 tion microscope can also be used. 



Bacterial attack can be observed very well 

 and very quickly Avith a phase contrast mi- 

 croscope. Staining methods also make the 

 bacteria clearly demonstrable, e.g., with 

 methylene blue or fuchsine (2-3 min.) or 

 with carbol fuchsine or carbol gentian violet 

 (20-30 sec). 



Finally, it should be stated that attack by 

 molds and bacteria can occur only if there is 

 sufficient moisture, whilst soluble nitroge- 

 nous material is likewise essential. 



Biological Attack. Biological attack is 

 largely accounted for by moths and the 

 larvae of the carpet beetle {Anthrenus ver- 

 hasci L.). Here again, it may be mentioned 

 that neither moths nor carpet beetles can 

 attack wool unless fats and salts are present. 



Attack by insects can be detected micro- 

 scopically immediately, owing to the typical 

 morphology of the damage. Moreover, 

 threads of the moth larva's web are often 

 present and beetles often leave hairs behind. 

 Diagnosis therefore causes no difficulty. 



Morphology of Fibers 



Silk (Fig. 2a). Raw silk consists of two 

 filaments of fibroin stuck together with seri- 

 cin. The filaments are triangular. Longitud- 

 inally, the fiber is very irregular. It shows 

 constrictions, creasing, folding and thicken- 

 ings. Both the shape and dimensions of the 

 triangular fibroin filaments are important. If 

 the cross section is slightly rounded the fibers 

 take dye less readily than the larger purely 

 triangular ones. 



Degummed silk is a smooth, almost struc- 

 tureless fiber. A barely visible longitudinal 

 striation can be observed. Zinc chloroiodide 

 sometimes stains silk fight yellow. In Mil- 

 Ion's reagent the fibers turn red. Provided it 

 is not weighted, silk dissolves in Cuoxam. 



Tussah silk (Fig. 2a). The filaments are 



flat and wide, show pronounced longitudinal 

 striation and cross-wise imprints of fiber in- 

 tersections due to the fibers hardening. Af- 

 ter maceration in cold chromic acid the 

 "fibrils" can easily be isolated. The diame- 

 ter of the fibrils is 0.3-1.5iu. Furthermore, 

 there is coarser striation caused by air canals. 

 The cross section is somewhat cuneiform. In 

 zinc chloroiodide the fiber remains colorless. 

 In Millon's reagent it turns red. In Cuoxam 

 it dissolves. 



Cellulose Fibers. Cellulose fibers may be 

 classified as bast, leaf, and seed. 



Bast fibers. This category comprises flax, 

 jute, hemp and ramie. The fibers are found in 

 the fibro-vascular region of the phloem. The 

 fiber bundles are bound together with cellu- 

 lar tissue and waxy substances. The fibers 

 are usually known as "soft" fibers. 



Leaf fibers. These are obtained from the 

 leaves of monocotyledonous plants. The fi- 

 bers occur in bundles, i.e., accumulations of 

 individual cells overlapping at the ends and 

 thus forming continuous filaments. These 

 cells are also held together by waxy sub- 

 stances. Unlike the bast fibers they are called 

 "hard." The complete bundles are used for 

 textile purposes. Most plants producing leaf 

 fibers are related. The main fibers belonging 

 to this group are sisal and manilla. 



Plant hair. The seed hairs of various plants 

 can be used for textile manufacture. The 

 main kinds used industrially are cotton, coco- 

 nut and kapok. 



Microscopic identification of the various 

 cellulose fibers is not particularly difficult. 

 Characteristics such as "fiber bundles," 

 shape of lumen, whether the lumen is air- 

 filled and the shape of the cross section are 

 adequate. 



For microscopic examination generally 

 only the ordinary light microscopic methods 

 are used. The electron microscope is used 

 only for fundamental investigation of the 

 cell wall. 



Cotton (Fig. 2b). The microscopy of cot- 

 ton is very important both as regards mor- 



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