On the Minute Structure of Striped Muscle, $<. 291 



needle. Under these circumstances, those fibres -which were pressed 

 upon lost their cross-stripes, and looked extremely like connective 

 tissue. Of course it might be urged that the fibres were by this 

 pressure entirely disorganised, and no conclusions can legitimately be 

 drawn from the. experiment, but to this it can be replied that if there 

 really are little bands of tissue so clearly distinguishable from each 

 other, as those who hold the MusJcelkdstchen hypothesis believe, these 

 or their traces should be found scattered about throughout the pre- 

 paration. In point of fact, as yon press upon the cover-glass the 

 stripings gradually disappear with increased pressure, and in the ill- 

 defined fibrillated structure that remains there are no traces of the 

 broken Muskelkastchen. And finally, if more proof is wanted, it is 

 possible by means of a screw, which raises or lowers the cover-glass, 

 first to press upon the fibres and cause the striping to disappear, and 

 then on raising the cover-glass to cause them to reappear once more. 

 We can only explain this result on the assumption that the varicose 

 fibrils are flattened out, and that the striping caused by their vari- 

 cosity disappears in consequence. 



There were, however, three important facts which had to be 

 thoroughly accounted for, before it could be affirmed that the fibrils 

 do not consist of the alternating structures supposed to exist ; these 

 facts were the effect of cleavage, of staining and the action of 

 polarised light. The muscle fibrils can be broken across into the 

 sarcous elements described by Bowman ; but a careful study of the 

 question soon convinced me that the cleavage is always across the 

 thinnest parts of the fibrils, taking 1 place in the substance of the clear 

 stripe. If Dobie's line is at all marked, the cleavage takes place near 

 the little swelling which corresponds to it, and through the substance 

 of the clear stripe. Reference to fig. 1 will at once show that here 

 we have to deal with the thinnest part of the fibrils, and it is there- 

 fore begging the question to assume anything over and above this 

 mechanical reason for the cleavage, for every varicose rod will break 



ross at its thinnest part. The phenomenon of transverse cleavage 

 cannot therefore be taken in itself as an argument in favour of 

 structural differences along the fibrils. 



The appearances seen in stained preparations can also, I pointed 

 out, be satisfactorily explained on the varicosity hypothesis. We 

 find that whatever else is employed, and at whatever focus you adopt 

 in your examination, those stripes which in the unstained preparations 

 appear dim also appear to take on the stain, while those stripes which 

 appear clear and bright are unaffected by it. In fact, the difference 

 in colour is entirely a question of " saturation," for whenever there is 

 a flood of light, as in a clear stripe, the colour of the fibre at that part 

 becomes unsaturated by it. It is easy to convince oneself practically 

 of this fact by the examination of varicose threads of faintly coloured 



