On the Mini it I', Structure of Striped Muscle, $-c. 299 



Fio. 4. 



drawing of a living and contracted Crab's muscle, which has been bent round 

 and artificially extended on its convex lower border. The transitions between 

 the relaxed and contracted parts are well seen. Dobie's lines (D) gradually 

 fade away as you pass to the contracted condition, becoming invested by and 

 then replaced by the dark stripe of the contracted condition. The dark stripe 

 of the relaxed part (_B) fades away, and is replaced by the light stripe in the 

 contracted part. 



any of the German histologists have described a condition observ- 

 able before the muscle has completely contracted (Uebergangsstadium), 

 irfcwhich all striping has disappeared, and this Merkel and Engelmann 

 each explains on his own imbibition theory. Now, one can dog- 

 matically affirm that in the greater number of fibres of which the tissue 

 is in one part contracted and another part relaxed, and in which the 

 intermediate stages are plainly visible, as in fig. 4, for instance, not 

 a trace of such a condition is visible ; it is therefore not an essen- 



lly intermediate phase. I have had the privilege of seeing 

 fessor Engelmann's preparations, and here it is seen, and in my 



n I occasionally come across it; but what I have invariably 

 observed is this, that it is never seen in a fresh preparation free and 

 unattached to cover-glass or slide. It frequently happens that fibres 



Jome pressed and otherwise fixed, and then it appears that when 

 y shorten, the contracted part pulls upon the still extended 

 portion, and diminishes by so doing the varicosity of the fibrils, and, 

 in. consequence, the striping which depends upon it. The effect is 

 ly the same as that produced by flattening out the fibres by 

 ssing on the cover-glass ; in one case the varicosity is diminished 

 obliterated by a pull in the length of the fibril, in the other case 

 y pressure applied to its sides. One may, at any rate, state that in 

 the vast majority of cases, as the varicosity becomes reversed, the 

 ils never become uniform threads of tissue, for, as the dim stripe 

 flattening out, eventually to form a depression, the clear stripe, 

 ;h Dobie's line still visible in its centre, is becoming a ridge. 



::: 



