MUSCULAR TISSUE. 



181 



4. The muscular tissue of the crayfish always has the 

 form of bands or fibres, of ver}' various thickness, marked, 

 when viewed by transmitted light, by alternate darker and 



ilHili^lssI 



Fia. 52. — Astac7(s fluviat'dis. — A, a single muscular fibre, transverse 

 diameter yigtli 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 fibrillse ; F, the 

 connection of a nervous with a muscular fibre which has been 

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

 of the fibrilljB ; n, nuclei ; nv, nerve fibre ; s, sarcolemma ; t, tendon ; 

 1 — 5, successive dark granular strias answering to the granular 

 portions, a, of each fibrilla. 



