194 



PRACTICAL HISTOLOGY. 



[xvr. 



fresh muscular fibres on a slide in normal saline, and across the 

 direction of the fibres place a hair. Cover, and press the cover-glass 

 down firmly on the fibres. The hair ruptures the sarcous sub- 

 stance, which retracts and leaves the tougher unbroken sarcolcrnma 

 between the ends of the ruptured fibre. Remove the hair, and 

 the now empty sarcolemma will be seen (fig. 167, C). 



(iii. ) Another excellent method is to leave the muscle in a 

 saturated solution of ammonium carbonate. The sarcolemma will 



FlQ. 167. A. Striped muscle of frog, sarcolemma raised' in the form of a bleb; B. 

 Ruptured fibre with sarcolemma ; C. Fibre ruptured by a hair ; D. Effect of acetic 

 acid on a muscle-fibre ; E. Muscle-discs. Ammonium carbonate. 



be seen raised for long distances from some of the fibres, with a 

 little of the sarcoglia sometimes adhering here and there to its 

 under-surface. 



2. Muscle-Corpuscles, or Nuclei (H). Tease a piece of a fresh 

 frog's muscle, and irrigate it with 2 per cent, acetic acid. I have 

 often found the nuclei beautifully stained in a piece of muscle that 

 has been in ammonium carbonate and then in picro-carmine. 



(a.) Observe the sarcous substance becoming swollen up and 

 more homogeneous, while a number of fusiform, somewhat shrivelled 

 or shrunken nuclei, with their long axis in the long axis of the 

 fibre, come distinctly into view. They are now slightly more 

 refractive than the altered sarcous substance, hence they are seen 

 with greater distinctness. Focus carefully, and note that these 

 nuclei lie not only under the sarcolemma, but also in the substance 

 of the fibres. Had a mammalian muscle been used instead of one 

 from an amphibian in the case of most muscles the nuclei would 

 have been found directly under the sarcolemma only. The presence 

 of the nuclei is merely revealed by the action of the acid, which 

 alters the refractive index of the sarcous substance, and thus brings 

 the nuclei into view (fig. 167, D). Sometimes faint longitudinal 

 striation is exhibited by such a fibre. 



3. Isolated Muscular Fibres. (i.) Pith a frog, and plunge it in 

 a beaker of water at 55 C. Leave it in the water, and allow the 



