376 Mr. J. B. Haycraft. Upon the Cause of [Feb. '3, 



bound together and seen on edge with the wavy outline towards the 

 eye of the observer, cross bands are seen which in chance prepara- 

 tions (especially those of the frog's lens) simulate muscle in a wonder- 

 ful manner. Ordinary non- striped muscle which may be so well seen 

 in the frog's bladder is often faintly ampullated especially, perhaps, 

 in chloride of gold preparations. Cross stripes may also here be seen. 

 The fibres of Tomes, when a section of softened tooth is teazed, are 

 pulled out of the dentinal tubules, and, being of a soft and somewhat 

 elastic nature, on breaking they become often very beautifully am- 

 pullated, and it would be impossible to distinguish them from muscular 

 fibrillse. In the class of practical histology, on more than one occasion, 

 students have asked me the meaning of beautiful cross shadings seen 

 on nerve fibres ; a slight ampullation which fully accounted for it, was 

 always found. 



Many more of such instances could be recalled in the experience of 

 every one ; it is needless to enumerate further. 



In the winter of 1879-80, while examining fibres of the muscles of 

 a newly-born child, a very curious discovery was made. A nucleus 

 belonging" to the sarcolemma was seen beautifully striped. It was 

 not in close apposition to the fibre, a very narrow chink intervening. 

 On focussing with great care, it was seen that the cross bands upon it 

 corresponded with those of the adjoining fibre, a dark one, however, 

 for a light one, and vice versa. (Fig. 6.) Now, the curious point was that 

 the nucleus had evidently been impressed by the fibre, moulded upon it, 

 as it were, and on being pulled apart had presented a perfect cast of 

 the surface. One would hardly believe in sarcous elements here. 

 Last summer (1880) my friend Mr. Priestley communicated to me a 

 similar and independent observation of his own, as a contribution 

 towards the maintenance of my views upon the formation of the 

 stripes. 



The position that we have reached is this : a muscular fibre presents 

 such cross markings, varying with shifting the lens up or down, as a 

 filament of homogeneous structure and similar shape. I have shown 

 this experimentally, and have illustrated it by simple experiments, 

 which it is in the power of anyone to test. This being the case, I 

 have searched to find if there be reason to assert any want of uni- 

 formity along the fibre, using various methods of staining. This I 

 have failed to do, and have shown that the views commonly held are 

 to be explained simply by the shapes of the fibres. As to the action 

 of muscle on polarised light, I saw reason to dissent from the views of 

 Briicke, and subsequently found my own in accordance with those of 

 other recent observers. I differ from them in the explanation I offer 

 of the two dark bands seen with crossed Nicols, for here, again, the 

 shape of the fibre explains their presence without looking for any 

 special structure. 



