648 Sir James Crichton-Browne [May 3, 



twine, spii-als which interlace. Interlacing spirals are seen in the 

 heart. The muscular structure of the heart, an asymmetrical organ, is 

 still in need of elucidation, but there can be no question that there is 

 at its apex a peculiar spiral concentration known as the vortex, or 

 whorl, produced by the twisting and interlocking of the external fibres 

 with those of the interior (Fig. 20). But if you interlace two spirals 

 one must lead ; they cannot l3e co-terminous ; and so if the cerebral 

 hemispheres are interlaced, and we can see their fibres crossing and 

 recrossing, one of them must lead. If you interlace the fingers, one 

 thumb must be uppermost, and in a great majority of persons it is 

 the right thumb that is so. Everyone has a fixed habit in this simple 

 matter from which it is uncomfortable to depart. 



It cannot now be doubted that right and left handedness are 

 dependent on cerebral organisation and on nothing else. But if we 

 go a step fm'ther and inquire how this cerebral organisation came 

 about, we are face to face with the inexphcable. We do not know 

 why the two hemispheres should have become unsymmetrical in their 

 convolutional arrangement, or in their pathways of intercommunica- 

 tion, why one should have become more voluntary, the other more 

 automatic ; why in an enormous majority of persons the left 

 hemisphere should lead the right ; why in a few persons the right 

 should lead the left. 



AYe can only fall back on cosmic principles and recognise a great 

 but obscure law regulating dextral and sinistral development throughout 

 the organic world. We find ourselves amongst those residual phenomena 

 that are not yet explicable in terms of chemistry or physics, pointing 

 to a directive force which enters upon the scene with life itself, and 

 which, while in no way violating the laws of the kinetics of atoms, 

 determines the course of their operation within the living being. We 

 find ourselves in the presence of a guiding principle or power that is 

 above and beyond the symmetric forces of inorganic nature. 



The asymmetry, or the one-sidedness of the brain, is a mystery, but 

 it is only one of a long series of mysteries of the same kind, and is 

 no more mysterious than the almost invariable position of the heart 

 on the left side and its occasional transposition to the right of the 

 median line. Indeed, when we come to look into it, it would seem 

 that all organic forms have been cast in an asymmetric mould, their 

 tissues being developed, from inherited asymmetrical beginnings in 

 the ovum or seed, or obtained by fission. 



I should like to trace back asymmetry through the organic world, 

 but time permits me to cite only one or two examples, and I cannot 

 select a more familiar one than that of the flat fishes — soles, plaice, 

 flounders, and so on (Fig. 30). A lady born and bred in London, told 

 me lately that until she attained mature age and married, she did not 

 know that there was such a thing as a flat fish in nature. She saw 

 them, of course, in the shops, but believing that all fish were of the 

 proper accredited symmetrical shape, like salmon, herrings or whiting, 



