39 



64. Fibrillae. (I^ongitudinal striations). Biceps of rabbit. 

 Treated with -^% platinum bichlorid 6-24 hours ; now in 82% alco- 

 hol. Carefully tease apart with needles the fibers of a shred of 

 muscle and stain 5 minutes with erythrosin ; dehydrate and clear. 

 On the slide in the clearer tease again, trying to split the individual 

 fibers ; you cannot tease too finely. 



If the teasing is fine enough in many places the fibers will be 

 separated into their component fibrillae. Observe this feature and 

 the structure of the individual fibrillae, the alternate light and dark 

 zones, lateral and transverse discs, the dark intermediate disc in the 

 midst of the light disc, and possibly the light middle disc in the 

 midst of the transverse disc. Ask the instructor to show you a 

 longisection of striated muscle stained with iron hematoxylin, in 

 which the discs are more sharply differentiated. 



65. Tendinous ends of muscle fibers. Cat. Intercostal 

 muscle, dissociated in nitric acid ; now in 82% alcohol. With the 

 needles gently separate the fibers of a small fascicle, taking care to 

 have the ends of the fibers well separated. If this is successfully 

 done, the continuity of fiber and tendon will be shown. Stain the 

 preparation with picrofuchsin five minutes, wash with 67% alcohol, 

 dehydrate, clear, and mount in balsam. The muscle fiber will be 

 stained yellow or orange, the tendon fibers red. Note the shape of 

 the end of the muscle fiber and its relation to the fibrous tissue of 

 the tendon. Can you determine the relation of the sarcolemma at 

 the end of the fiber ? 



66. Anatomy of a skeletal muscle. Obtain from the desk 

 an entire muscle which has been macerated in 20% nitric acid. Dis- 

 sect it carefully, determining the course and arrangement of the 

 component muscle fascicles in relation to the tendons (if present) of 

 origin and insertion. Are the fascicles parallel with the axis of the 

 muscle ? Is it a penniform- or bipenniform muscle ? 



67. Transection of a skeletal muscle. Cat. 



; collodion ; sections /x. Stain with hematoxy- 



lin 15 minutes, picrofuchsin 30 seconds. Mount in balsam. 



Observe the connective tissue sheath of the muscle, the epi- 

 mysium, the transected muscle fascicles surrounded by the perimy- 

 sium, the individual fibers held together by the endomysium ; finally, 

 in the transection of the fibers, note the punctate appearance of the 



