78 TRANSVERSELY STRIPED MUSCULAR FIBRES. 



individual transverse striee ; under favourable illumination, and by 

 the help of the diaphragm, the flat sections are seen to present a 

 net-like appearance, resembling lines which intersect one another 

 at acute angles, and are somewhat swollen at the points of inter- 

 section. The transverse separation of the muscular fibres may 

 often be recognized by the fact, that the half only of a disc cor- 

 responding to the transverse cleavage is torn off, whilst in some 

 cases one of the transverse discs of a muscular fibre is loosened 

 and coiled back on itself ; or again, a muscular fibre is somewhat 

 bent and torn up at its convexity into separate transverse discs, 

 causing them to diverge like the leaves of a badly bound open 

 book. (F.P. 15, F.4.) 



Concentrated acetic acid produces the same effect after from 

 5 to 10 hours' action, as the dilute acid does in a much longer 

 period. 



The sarcolemma is not altered either by dilute or concentrated 

 acetic acid ; at the parts where it has been deprived of its contents, 

 it presents the appearance of a structureless membrane without 

 nuclei, but interspersed at different points with fat-globules. 



Very dilute hydrochloric acid (\ part of acid in 12,560 parts of 

 water) produces nearly the same effect on the muscular bundles as 

 acetic acid, rendering them paler, whilst the nuclei come promi- 

 nently forward; the muscular fibres do not, however, swell to so 

 great an extent as when dilute or concentrated acetic acid is used ; 

 the transverse striations are sharply marked, but a transverse 

 cleavage of the fibres is not so frequent ; there is no appearance 

 of longitudinal striations (primitive fibrils). "The mode of action 

 of a less dilute hydrochloric acid will be considered at a subsequent 

 page. 



Donders* maintains that by prolonged digestion in dilute hydro- 

 chloric acid, the sarcolemma (at all events, in the primitive bundles 

 of the heart) is rendered very distinct. 



Concentrated hydrochloric acid converts moderately sized pieces 

 of muscle, after a short time (8 hours), into a viscid mass, which 

 can be easily stirred in the fluid surrounding it. We discover 

 under the microscope, that the fluid contains rather short parallelo- 

 pipeds, having a very distinct and often sharply defined transverse 

 striation. Although longitudinal striae may be detected here and 

 there in the fibres, the primitive bundles are only torn or cleft 

 in a transverse direction ; but whilst the transverse striee always 

 follow a tolerably parallel course, they frequently exhibit several 

 * Nederlandsch Lancet. 3 S. 1 J. S. 559. 



