On the Minute Structure of Striped Muscle, Sfc. 289 



Personal Observations lefore the Year 1880. 



More than ten years ago it was my duty, as a young teacher, to 

 make myself familiar with the current literature bearing upon the 

 structure and function of muscular tissue. Even then the number of 

 publications was very great, and I can now recall the despair with 

 which I tried to get a grasp of a subject about which no two observers 

 could be found to agree. While endeavouring to verify some of 

 the statements I had read, I found out for myself that the fibrils are 

 iu reality varicose threads of tissue, presenting alternate swellings and 

 constrictions of their substance. At once the conviction forced itself 

 upon my mind that the striping might after all be an optical expres- 

 sion of the form of the fibrils, and have nothing whatever to do with 

 their internal structure ; and it was not until my results were in 

 manuscript form, and ready for publication, that I got access to the 

 older and almost forgotten literature in which I found the same 

 views freely expressed, although without any attempt at their proof. 



When I had made certain that, both in the fresh, and in the prepared 

 muscle, the fibrils are invariably varicose, then I felt that the position 

 of the subject was as follows. Such fibrils are bound to be cross- 

 striped like all other objects of similar shape, viewed by transmitted 

 light. It may be that the cross-striping observed is due to the vari- 

 cosity alone, or to the varicosity and to .co-existing structural differ- 

 ences as well ; and, under these circumstances, before we are in a 

 position to take any further step in an investigation into the nature 

 of the muscular fibre, it is imperative to eliminate the appearances 

 due alone to varicosity. 



My first endeavour was to ascertain whether there are any stripes 

 that do not correspond in their position with inequalities in the thick- 

 ness of the muscular fibrils. 



Of course in many cases it is difficult, especially if the fibrils or 

 fibres are somewhat distorted, to make out the border clearly ; but in 

 good specimens, in a suitable position for study, I found that the 

 striping, both in the contracted and uncontracted fibre, corresponds 

 invariably to either thickenings or constrictions of the fibrillar sub- 

 stance, and in this investigation the muscular tissue of many repre- 

 sentative species, both Vertebrates and Invertebrates, was examined. 

 The broad dim stripe occupies the position of a thick bulging part of 

 the fibre, and Hensen's stripe, when present, corresponds to the posi- 

 tion of a shallow depression in its centre. The clear stripe lies in the 

 constrictions of the fibril and Dobie's line corresponds with a tiny 

 swelling in its centre. 



In addition, the stripes can be reversed by altering the focus, just 

 as is the case with a little varicose glass thread, the scale of a Lepisma, 

 or the shadow in the centre of a red blood-corpuscle ; indeed Bowman 



