F1B^:KS (TEXTILE) 



sharp razor blade. The cut surface is now 

 examined under a microscope without fur- 

 ther preparation. 



(2) Hardy Microtome. Relatively thin 

 sections can be made with this simple in- 

 strument. It consists of two rectangular 

 plates held together by lateral ridges. In the 

 middle of one plate there is a very narrow 

 slot. From the middle of the other plate a 

 thin metal lip protrudes which fits exactly 

 into this slot. If the two plates are fitted to- 

 gether a very small part of the slot remains 

 open. By means of a micrometer screw" a 

 second metal lip can be pressed into this 

 open part from underneath. 



In order to make a section, the slot is filled 

 with a bunch of fibers. Next, the second plate 

 is affixed. The fibers are severed with a razor 

 blade above and below the plate. The mi- 

 crometer screw is fitted in such a way that 

 the lip is immediately under the slot. By 

 means of this, the bunch of fibers can now 

 be pressed several microns out of the slot. 

 After the protruding fibers have been coated 

 with cellulose lacquer, the cut is made with 

 a sharp razor blade pressed as close to the 

 plate as possible. 



Sections of lO^u can easily be made, and 

 with sufficient experience sections of 3ju are 

 not unusual. 



(3) Freezing Microtome. If a bunch of 

 fibers is imbedded in celloidine or gelatin, it 

 it possible to make a l-dfj. section with a 

 sledge freeze-microtome. On the whole the 

 sections are more regular than with the 

 previous methods and hence more suitable 

 for examination with phase contrast and in- 

 terference microscopes. 



Making Longitudinal Sections. If a bunch 

 of fibers laid exactly parallel is mounted in 

 gelatin, thin longitudinal sections can be 

 made therefrom with a sledge freeze-micro- 

 tome. It is essential for the knife to be mov- 

 able W'hile the specimen holder is stationary. 

 It must, however, be possible to set the 

 holder three ways relative to the knife. 



If a freezing microtome is not available. 



it is quite possible to make good longitudinal 

 sections with Stove's method, as follows: 



A cellulose acetate film is applied to a 

 slide. This film is moistened with xylene. On 

 top of this a bunch of fibers is laid exactly 

 parallel. It is advisable to apply some ten- 

 sion by affixing a 2-gram weight at each end 

 of the bunch. When the xylene has evapor- 

 ated, a drop of ethyl lactate is added, while 

 next a solution having the following compo- 

 sition is applied in abundance: 



The whole must then dr^^ for 36 hours at 

 room temperature and can next be mounted 

 in paraffin with a melting point of 50°C. It 

 is better to use a mixture of paraffin and bees- 

 w^ax, the hardness then being adapted to that 

 of the fibers. 



Surface Examination. The surface struc- 

 tures of fibers can be examined by the fol- 

 lowing methods: (1) replica, (2) semi-embed- 

 ding, (3) interference microscopy, and (4) 

 electron scanning method. 



(1) In the repUca method, cellulose ace- 

 tate (12 g) is usually used, dissolved m ethyl 

 lactate (10 ml) and amyl acetate (78 ml). 

 A film of this solution is made on a slide by 

 the smear method customary for microbiol- 

 ogy. The fibers are placed carefully on this 

 film. After about 30 min. they can be pulled 

 off the film. The replica can be examined 

 forthwith under a microscope. Instead of 

 cellulose acetate solution a normal cellulose 

 lacquer can be successfully used. 



(2) In semi-embedding, the fiber is care- 

 fully pressed into a swollen film with about 

 the same refractive index as the fiber. In 

 the microscopic image the hifiuence of the 

 lower half of the fiber is thus eliminated. 



Protein glycerin can be effectively used for 

 protein fibers. For wool and keratin fibers 

 ROX 1 (Chroma) is particularly suitable. 

 For cellulose fibers ROX 2 (Chroma) or 

 cellulose lacquer may be used. 



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