290 



MANUAL OF HISTOLOGY. 



Fig 282. Portion of 

 dead muscle fibre, 

 after Englemann. a, 

 transverse disks; 6, 

 accessory disks. 



This does not appear to be the place for entering more deeply into the 



subject. 



The structure of striped muscle fibres will probably remain a matter of 

 controversy for many years to come. We look, however, 

 upon the cross-lines of Krause as fully substantiated. 

 But as to the existence of lateral membranes, and the 

 theory of the u muscle caskets" dependent on it, we do 

 not believe in it any more than in the fluidity of 

 the cementing medium. As regards the middle disks, 

 we have not yet come to any definite conclusion. We 

 look upon the sarcous elements as pre-existing in some 

 form or other, and not as products of coagulation 

 (Engelmanri). In our opinion the longitudinal fibrillae 

 are artificial productions. 



Unexpected results were obtained some years ago by a method of treat- 

 ment practised by CoJmheim, namely, the preparation of transverse sections 

 of frozen muscle. In these may be recognised groups 

 of sarcous elements, like a mosaic of small par- 

 ticles of from three to six-sided figures. Between and 

 bounding these is a trellis-work of transparent glit- 

 tering lines, which become broader only at irregular 

 intervals. These belong to the transverse cementing 

 medium. 



It is still a matter of uncertainty whether the ele- 

 ments of unstriped muscle possess sarcous elements or 

 not. 



Bruclte made a very interesting discovery long ago, 

 namely, that Bowman's sarcous elements, together 

 with the cross-lines of Krause and middle disk, are 

 double refracting, and are positively monaxial, while 

 the cement deposited between them is single refracting. 

 The first are " anisotropic," the latter " isotropic." 

 The correctness, however, of Bi-iicke's statement has 

 been since questioned by Rouget and Valentin. 



REMARKS. 1. The slight inclination of the fibrillae to separate from one another 

 (when no reagents are made use of) seems also to point to this conclusion. 2. " The 

 muscle fibre is therefore just as little a bundle of fibrillfe as a pillar built up of disks 

 arranged one over the other. Should a total separation in both directions really take 

 place, the result would necessarily be a breaking up into fleshy prisms." " And if we 

 tear off a fibril from a muscle fibre we take away from every disk a sarcous element, 

 and vice versa" (Xowman). 3. Dobie (Annal. of Nat, Hist., Feb. 1848) also discri- 

 minated m the same manner long ago between the darker sarcous elements of Bow- 

 man and a second system of clearer portions situated between them. Muscle fibres, 

 when stretched, show, according to Martyn (Scale's Archives, Vol. iii. p. 227), another 

 transverse line passing through the centre of each clear zone. The same was pre- 

 viously observed by Amici, Koelliker, and others. I myself have remarked it 

 frequently too. 4. They may assume very large proportions, also, in the crawfish. 

 > they were found by Hakel to vary from 0'0020 to 0'0099 mm. in height ; and 

 ic was able to isolate them in a gelatinous condition as long as 0' 0114 mm. He looks 

 upon them as hexagonal prisms. Amici s observations are also of great interest. 

 According- to him, the elongated prismatic elements ot the muscle of the common 

 s-ny, separated by a distinct cement or clear zone from one another, assume 

 during contraction a marked obliquity of position. This I can corroborate myself, 

 lurther, according to Schonn, there is a dark spot visible in each sarcous element. 



Fig. 283. Transverse 

 section of a frozen 

 frog's muscle. o, 

 groups of sarcous ele- 

 ments ; 6, a nucleus ; 

 c, clear cement. 



