i ORGANISATION AND STRUCTURE OF MUSCLE 43 



Hence in cross-section (Biedermann, Thin, Gerlach, Ketzius, and 

 others), Cohnheim's are<e stand out colourless from the very 

 distinct red plexus of the sarcoplasm. The longitudinal section 

 of fibres treated with gold is no less divergent. Gerlach, who 

 investigated vertebrate muscle only, characterises it as " speckled "j_ 

 each fibre appears interspersed throughout its thickness with a 

 crowd of dark, red or black, dots and streaks, which, as Gerlach 

 correctly observed, give an impression of continuous and often 

 varicose fibres in places, and are only too easily mistaken for fine 

 nerve-fibrils (Fig. 28). The gold chloride figures of Arthropod 

 muscles are generally much more regular, r,, j 



and accordingly present less ambiguous /# -jl 



conclusions. /'/';'( ... 



Before discussing these facts, it is Mi' j 'i \\\\\\ li'-.lV'' --/f 

 advisable to consider briefly the simple jji./J/ 



action of acids, since this is always ^\i', jj/ 



combined with the gold method. The 

 first effect of treatment with very weak i|j| 

 acids (acetic, formic, haloid, etc.) is best 

 exhibited in muscle-fibres which have jiilj 

 lain in strong alcohol (93 / ) for 

 twenty-four hours. The earliest and /;[' 

 most striking changes occur within the 

 system of strise (Q h Q), which swell 

 up, and seem to bulge out from the 

 wall of the fibre (or muscle -column). 



mi n T FIG. 28. Surface of muscle - fibre 



This process may go so far, on apply- (Frog) treated with gold chloride 

 ing a somewhat stronger solution, as to to show Geriach's " speckles." 



rv> TIT;,- i (Biedermann.) 



enect radical alteration in the striae 



(N Z), which lie, as it were, crushed in between the much- 

 broadened and now homogeneous (Q) bands (Fig. 29). 



On the other hand, the rapid swelling of the segments (Q li Q) 

 at a still more advanced stage of the acid reaction may produce 

 an explosive disintegration of the muscle-fibres into discs, by a 

 process of continuous splitting up within (Q), by which the 

 segments (JN E, Z, E N J) are finally driven apart, and isolated 

 as discs. It would follow that the changes which the longitudinal 

 section of the muscle-fibre undergoes during the action of strong 

 acids are to be referred partly to changes of form in the muscle- 

 columns (or fibrils), due to differences of turgescence in the indi- 



