Orientation of Fibrils in Natural Membranes - Nature

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Abstract

IN recent years, several studies of the orientation of chitin and protein chains in the insect cuticle^1,2 and of cellulose chains in plant cell walls³ have appeared. Between 1938 and 1940, X-ray, optical and chemical studies of the cuticle of annelids and nematodes were made by one of us (L. E. R. P.) with the idea of obtaining information about the structure of other types of natural membranes. The cuticles of these animals are largely composed of fibrils of a protein belonging to the collagen group, distributed with their long axes in the plane of the cuticle and in two preferred orientations with respect to the long axis of the body. In annelids, such as Aphrodite and Lumbricus, the fibrils cross at c. 90°, and each set makes an angle of c. 45° with the long axis. In Ascaris, the two sets make an angle of c. 135° with each other and of c. 70° with the long axis. An arrangement of this kind may be mechanically advantageous, since the resulting membrane is capable of anisometric extension, though the individual fibrils are inextensible.

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