SPECIAL METHODS 



acteristic crystal growth "whiskers" sug- 

 gested by Sears (8), and (b) the tem- 

 perature rise of the specimen caused by 

 electron irradiation, which it was hoped 

 could be checked by observing the hquid- 

 solid phase transition. Fig. 12 (a) shows 

 hair-like crystals formed by condensing 

 mercur\^ vapor at about — 100°C. (b) was 

 taken two minutes after (a). The crystal in- 

 dicated by the arrow completed its growth 

 within a fraction of a second. Fig. 13 (a) 

 shows a droplet of liquid mercury. This drop- 

 let was formed at -39° to -38°C by heat- 

 ing the solid state crystal. This droplet of 

 liquid mercury was poligonized through crys- 

 tallization at about — 100°C as shown in 

 (b). 



Study of Natural Cellulose Fiber (9). The 

 atomic structures of an organic substance 

 like cellulose fiber are so hable to be dam- 

 aged by irradiation of electron beams that 

 the diffraction patterns can be observed for 

 only a very short time. We can avoid this 

 difficulty by using a method of cooling the 

 specimen. Fig. 14 reproduces two pairs of 

 electron micrographs and diffraction pat- 

 terns of Valonia microfibril taken by 

 Boersch-le Poole's method ; (a) and (b) were 

 taken without cooling and (c) and (d) by 

 cooling the specimen to — 40°C. This speci- 

 men is composed of two sheets of microfibril 

 having fiber axes along the directions indi- 

 cated by the arrows. In the electron diffrac- 

 tion patterns of Valonia microfibril cooled 

 to — 100°C taken by Hilhers method, a very 

 large number of reflections having fairly 

 good resolution up to as high as tenth layer 

 line has been observed. By analyzing these 

 patterns, the new structure different from 

 that proposed by JNIeyer and Misch (10) for 

 cellulose I has been obtained. 



Specimen-Heating Method 



The specimen heating method makes it 

 possible to observ^e continuously the change 

 of a specimen at high temperature, by at- 

 taching a heating furnace of a specimen to 



ordinary electron microscope. This method 

 is divided into two parts: (1) in which a heat- 

 ing device with a small electric furnace is 

 used for both reflection and transmission 

 (11, 12) and (2) in which the temperature 



Fig. 12. Hair-like cry.stal.s of mercury, (above) 

 Hair-like crj-stalso frmed Vjy condensing mercury 

 vapor at about — 100°C. (below) Two minutes after 

 picture above. 



Fig. 13. Mercury droplet, (above) Liquid state, 

 (below) Solid state, crystallized at about — 100°C. 



265 



