136 MANUAL OF HISTOLOGY. 



wave enter into the contracted condition, those behind as- 

 sume their normal state at first, but do not retain it, for they 

 are immediately subject to a severe stretching by the course 

 of the wave, and present 'new and very instructive appear- 

 ances. The fibre becomes much narrower, the black stripes 

 are resolved into two rows of granules some 

 distance apart. The whole substance of the 

 fibre is lighter than in the other conditions, 

 and though the bright borders of the stripes 

 are still there, they are much less glaring, and 

 present less contrast with the intermediate por- 

 tion. 



In some of these fibres an indistinct longi- 

 tudinal striation is seen, but the writer is not 

 satisfied that it is in the substance of the fibre. 

 _ Transverse sections of muscle have been ap- 



Fio. 58. Trans- 



verse section of frozen p ea i e d. to for elucidation of the structure of the 



frogs muscle show- f 



irvgcohnhetm's areas. gb re> Cohnheim showed B, network of whitish 

 lines surrounding small, dull-colored polygons 

 on cross-cuts of frozen muscle (Fig. 56). The muscles of the 

 crab are said to show this particularly well. Schafer found 

 in the muscles of the water-beetle the appearance of granules 

 on a clear ground. A similar appearance is seen in the fibres 

 of vertebrates. The writer has observed in the cross-section of 

 fibres from the tongue of the mocassin snake, granules which 

 presented, at least, the suggestion of bright points in their cen- 

 tre. In some fibres these were collected into groups, separated 

 by clear spaces. 



Cohnheim's areas cannot be considered equivalent to fibril- 

 lae, but rather, as Kolliker claims, to bundles of them, sup- 

 posing always, we would add, that fibrillse exist at all. It is 

 pointed out in the account of the transverse striae that these 

 are often interrupted, and there is no doubt that this may be 

 due to the limits of the muscle-columns. Of course, we must 

 assume that there are many more columns than would be in- 

 ferred from these interruptions ; for if the transverse stripes of 

 two neighboring columns exactly correspond, no break will 

 appear. 



Nuclei and muscle-corpuscles. In mammalian muscle acetic 

 acid demonstrates a number of oval nuclei which may contain 

 one or more uucleoli. Their long axis runs in the same direc- 



