MUSCULAR TISSUE. 



181 



4. The muscular tissue of the crayfish always has the 

 form of bands or fibres, of very various thickness, marked, 

 when viewed by transmitted light, by alternate darker and 



FIG. 52. Astacns flHtiatilis. A, a single muscular fibre, transverse 

 diameter T Lth of an inch ; B, a portion of the same more highly 

 magnified ; C, a smaller portion treated with alcohol and acetic 

 acid still more highly magnified ; D and E, the splitting up of a 

 part of a fibre, treated with picro-carmine, into fibrillae ; F, the 

 connection of a nervous with a muscular fibre which has been 

 treated with alcohol and acetic acid, a, darker, and #, clearer portions 

 of the fibrillas ; , nuclei : ni\ nerve fibre ; <<?, sarcolemma ; t, tendon ; 

 1 5. successive dark granular striae answering to the granular 

 portions, a, of each fibrilla. 



