Plate 1 



A. The a-type X-ray diffraction pattern. Material mohair, fibre to plate 

 distance 4 cm, Ka radiation. For a description see pp. 14 and 17. 

 The strong meridional arcs corresponding to 5-1 A on the vertical axis 

 and the very strong reflections ( ~ 10 A) on the equator are the two most 

 characteristic features. Strong spacings may be seen on the equator cor- 

 responding to 27-30 A and on the meridian a series of faint " long 

 spacings " can be seen. Fibre axis vertical. 



B. The /3-type X-ray pattern given by stretched and set fibrous keratins 

 and other a-proteins (stretched Lincoln wool). The 5-1 A reflection of 

 o:-keratin is missing and a further arc (3-5 A) has appeared. On the 

 equator strong reflections at 4 -5^1 -6 A are present. Other reflections on 

 the layer lines may be made out. 



Both fibre patterns are overlaid by a wide diffuse halo centred about 

 4-2 A. 



Photographs kindly lent by Mr. H. J. Woods. 



