40 PRACTICAL HISTOLOGY. 



the muscle-fibre is divided into a series of compartments, each containing a dim disc with a 

 lateral disc attached to each end. In this preparation no nuclei are seen. {Indicate these discs 

 in PI. VII., Fig. II.) 



Logwood and Dammar Preparation (H). The dim discs are logwood-coloured the light 

 discs unaffected. In the course of the fibre are seen oval nuclei under the sarcolemma. 

 Otherwise the details are the same as in the above preparation. 



If the muscle of an insect say hydrophyilus or dytiscus be taken and similarly treated, a 

 row of fine granules is observable in the lateral discs. These form the granular layer of 

 Flogel. 



LIVING MUSCULAR FIBRE. 



PREPARATION. This is not particularly well adapted for a large class of students. Cut 

 off the head of a water-beetle ,and then open its chitinous body with a sharp-pointed pair of 

 scissors, so as to expose the large wing-muscles. Snip off a small piece of these and tease it 

 rapidly in aqueous humour (p. xxx) or salt solution (p. xxx). Cover and examine. 



EXAMINATION (H). Observe the fibres, their striation, and that they are soft and plastic. 

 Here and there a thickening, progressing along a fibre a contraction-wave with approxi- 

 mation of the discs, may be observed. 



NUCLEI OF MUSCLE. 



PREPARATION. Take a small piece of a muscle of a rabbit or cat which has been pre- 

 served in alcohol, tease it out in water, and stain it in carmine till it is of a bright red 

 colour. Wash it in water to remove the surplus carmine. Place on it a large drop of glacial 

 acetic acid, and after doing so examine it with a low power, to notice when the nuclei alone 

 remain stained. The effect of the acid is to remove the diffuse staining, and leave the carmine 

 only in the nuclei. Mount it in either Farrant's solution or dammar preferably the latter. 



EXAMINATION (H). Observe the striation, and in the course of the fibres oval nuclei 

 with their long axis in the axis of the fibres, stained deeply red. (Indicate the nuclei in PI. VII., 

 Fig. 8.) 



Relation of the Nuclei to the Sarcolemma. Take a limb-muscle or the tongue of a cat 

 or rabbit or other animal, previously hardened in alcohol, or chromic acid and alcohol (p. xxxi), 

 and make a transverse section by freezing or other means. Stain it for a few minutes with 

 logwood and mount it in dammar. This preparation will also show the relation of the 

 connective tissue, or perimysium, to the muscular fibres. 



EXAMINATION (L). Notice the connective-tissue perimysium of a light blue colour 

 surrounding groups of muscular fibres cut transversely, which appear as small polygonal areas 

 stained light blue. (Indicate tlie connective tissue, and the ait muscular fibres with their nuclei 

 in PI. VII., Fig. 12.) 



(H). Observe the cut ends of the fibres, each more or less polygonal, through mutual 

 pressure of the fibres against each other. Under the sarcolemma are seen two or more small 

 logwood-stained nuclei in each fibre, and the cut end of the sarcous substance appears slightly 

 dotted. The nuclei are often situated at the angles of the polygon. Trace the connective 

 tissue in very fine strands between the fibres forming the endomysium and, it may be, con- 

 taining a capillary here and there. In a transverse section of a frog's muscle nuclei are found 

 to exist, not only under the sarcolemma, but also throughout the sarcous substance. 



