428 SECTIONAL TRANSACTIONS.—A. 
Joint Discussion with Section K (Botany) on The X-ray analysis of 
fibres (11.0) -— 
Mr. W. T. AstBury.—Some recent developments in the X-ray inter- 
pretation of the properties of hair, feathers and other protein 
structures. 
The recognition by X-ray methods of the regular, side-to-side cohesion of 
long, chain-like molecules to form crystalline bundles has served to give 
form to existing physico-chemical data, and helped us to understand for 
the first time many of their most characteristic properties. In particular, 
it has been found possible to follow changes under applied stress and 
chemical treatment of the configuration of gigantic protein molecules, such 
as those of the keratin of hair and feathers, and thereby to study the molecular 
mechanism of their long-range elasticity and link it up with that of simpler 
molecules. The crystal analysis of the chain-bundles involves at the outset 
some generalisation of the usual geometrical treatment, with the result that 
we are led to the concept of standard average dimensions of intra-molecular 
units, from which can be predicted the probable density of proteins as a 
class and the weight per unit area of mono-molecular protein films. Devia- 
tions from these standard average dimensions, as in the case of gelatin, may 
be used to investigate the linkages which give rise to them and ultimately, 
it may be hoped, to derive the precise form of the intra-molecular pattern, 
while from a knowledge of the molecular direction associated with each 
particular dimension we may follow the course of localised reactions such 
as the attack of water on the protein side-chains. The interaction of water 
with protein and other chain-bundles offers points of considerable interest, 
especially when studied in relation with their elastic properties. 
Dr. R. D. Preston.—The structure of the cell wall of Valonia. 
While the cells of most species of Valonia are approximately isodiametric 
and are not to be considered as fibres in the morphological sense, their walls 
are certainly composed of molecular fibres such as are typical of the true 
fibres of the plant. Sufficient work has already been carried out to indicate 
the importance of investigations on the walls of these large cells in relation 
to the organisation of the walls of what may be called the ‘ obvious ” fibres. 
The wall of Valonia consists of a kind of molecular basket-work over the 
whole surface composed of two sets of cellulose chains, crossing at about 
80° to each other, which have been shown to be parallel to the two sets of 
striations visible under the microscope. These chains of cellulose exist in 
the form of well-defined crystalline aggregates whose orientation is usually 
remarkably perfect. As observed by Sponsler, the planes of ‘spacing 
6-1 A. tend to lie parallel to the surface of the wall, though there exists an 
undoubted dispersion. Variation of the relative amounts of the two sets 
of chains from point to point in the wall gives rise to a somewhat misleading 
heterogeneous appearance in the polarising microscope. 
The structure of the cellulose net of the whole wall is now being mapped 
out by a ‘ lines of force method,’ and it seems highly probable that the 
crossed chains observed at any point are portions of two spirals. 
Dr. J. B. SpEAKMAN.—Fibre chemistry and X-ray analysis. 
Wool fibres may be stretched as much as 70 per cent. of their length in 
cold water without losing the power of returning to the original length. 
If, however, stretched fibres are exposed to the action of steam for, say, 
six hours, they assume a ‘ set ’ which is not eliminated even by re-steaming 
