On the Minute Structure of Striped Muscle, SfC. 295 



preparation be used for stamping, makes its own individual impres- 

 sion in the collodion, which rises between the fibrils in the place of 

 the interfibrillar substance, which has, of course, been removed in the 

 ordinary preparation of the tissue. When the muscle is pulled away 

 the impressions of the individual fibres can readily be made out, and 

 the borders of the little varicose hollows are plainly to be seen ; the 

 cross-striping, which can here only be due to the form of the impres- 

 sion, is exactly the same as that of the muscle itself. To put it in 

 another way, we have varicose threads of air, within surrounding 

 collodion in the place of varicose threads of muscle surrounded by 

 balsam or Farrant, and varicosity, the only common factor in the two 

 cases, is alone the cause of the striping observed in each. Not only 

 are the broad stripes well marked, but one can see with even greater 

 ease than in the muscle itself the lines of Dobie and of Hensen. 

 In the fresh muscle I have only once or twice seen the outlines of the 

 fibrils with any degree of distinctness, but the stripings are more 

 readily seen ; yet one would hardly expsct to get such good results 

 from fresh muscle, both on account of its softness and from the fact 

 that the fibrils are covered by sarcolemma. If the collodion be tinted, 

 say with magenta or Bismarck-brown, impressions can be made in 

 this coloured medium, and these show in beautiful detail the apparent 

 stain differentiations observed in muscle. The broad dim stripe 

 comes out red and appears like a solid, well-defined band, and the 

 clear stripe in successful preparations appears by contrast devoid of 

 colour. 



It will be seen from the above experiments that, as the stripings 

 are all optical effects of varicosity, the very foundations of the 

 Muskelkastchen hypothesis are removed, and we now come to the 

 consideration of the phenomena of contraction. 



An " impression " of a muscular fibre shows in evert/ detail the appear- 

 ances characteristic of the muscle used to stamp it, in whatever state of 

 contraction or relaxation it may happen to be. If a piece of muscular 

 tissue, hardened in alcohol in the extended position, be examined 

 under the microscope and its details studied, and if an impression of 

 it be then made, the impression will show the same details that it 

 shows. The same holds good for the contracted or semi-contracted 

 fibre. Photograph I was very kindly taken for me by my friend Dr. 

 Carrington Purvis, and shows the appearances presented by a Crab's 

 muscle in a state of extension. The little varicose fibrils are seen 

 separated by little varicose dark lines, the latter being the optical 

 sections of the interfibrillar substance. 



Photograph II* is taken from an " impression " of a muscle in a 



* The photographs of the " impressions " were taken by my friend Dr. Eding- 

 ton, to whose skill and interest I am much indebted. As the " impressions " only 

 last about five or six minutes, and as with ordinary illumination an exposure of 



VOL. XLIX. X 



