Dr. .1. I'. H.-.yrraft. 



similar condition, and it will be noticed that tin- appearance is 

 essentially the same, except that the stripes are reversed, the little 

 dots forming Dobie's line and the dim bands coming out bright, and 

 the clear stripe appearing dark; the slightest alteration of the 

 would have reversed the photograph and have given the ordi 

 appearance. 



A contracted fibre has quite another appearance, for not only 

 the cross-stripings much nearer together, but they have changed 

 character. Without going into detail, at present, it is sufficient 

 say that alternately dark and light stripes are seen, and that 

 Dobie's line, so constant a feature in the extended fibre, is 

 longer to be seen in the contracted condition ; the stripes, moreovi 

 have altered in thickness relatively to one another. Now it is n 

 less to again point out that the change in the striping has hithe 

 been held to indicate changes within the fibrils of the nature 

 osmosis, the stripes being taken to represent actual structures. Bo 

 if an impression be taken of a muscle killed in contraction it showi 

 every detail of a muscle in that condition, as photograph III, tak 

 from a collodion impression, very well indicates. (In this photogra 

 the clear stripes come out clear, and the dark stripes dark, just as 

 the original muscle, but of course the appearance could be reve: 

 by altering the focussing.) 



It follows that when a muscle passes into a condition of contracti 

 the changed appearance is entirely due to a change in its form, and 

 I have frequently stamped muscles which show in the same fibre boi 

 the contracted and uncontracted state with the intermediate s 

 These intermediate changes come out perfectly in the " impressions,' 

 so that one can positively affirm that the striping is due to form, 

 every change in striping observed during contraction depends upon 

 some change of form too. Of course the imbibition theories of 

 Kranse, Merkel, and Engelmann are no longer tenable, since the facto 

 on which their theories were founded have received another explana- 

 tion. The Muskelkastchen was evolved on the supposition that the 

 cross stripes correspond to membranes and layers of tissue along the 

 fibres, whereas the impressions prove that they are due to variations 

 in the thickness of the fibrils in different parts of their course. The 

 imbibition theories were evolved on the supposition that the changes 

 in the striping observed during contraction are due to alterations in 



from ten to fifteen minutes is required, our first attempts were not as successful as 

 might huve been desired, and those exhibited in Berlin were decidedly faint and 

 wanting in density. Dr. Edington subsequently, adopting a suggestion of Mr. 

 Forgan, used magnesium light in the place of the ordinary oil lamp, burning about 

 one foot of the thin riband in the optical axis of the apparatus. This exposure, 

 lasting only a few seconds, gave us very beautiful negatives, from which tin- photo- 

 f riTure plate was taken. 



