MUSCULAR TISSUE. 37 



EXAMINATION (L). Observe the large number of nuclei stained either blue or red, lying 

 usually in one plane. 



(H). Observe the shape and disposition of the long fusiform nuclei. Many of the cells 

 are fusiform, but others are tri-radiate. 



T. S. OF NON-STRIPED MUSCLE. 



PREPARATION. Place a piece of the muscular wall of the intestine of a cat in chromic 

 acid and spirit solution, and after two weeks make transverse sections of its circular muscular 

 fibres. Stain a section with picrocarmine for twenty-four hours and mount it in Farrant's 

 solution. Stain another with logwood for five minutes, and mount it in dammar. 



EXAMINATION (H). Observe the field mapped out into small polygonal areas of different 

 sizes. These are the fibres cut across. These areas occur in groups of small fasciculi, sepa- 

 rated from each other by connective tissue, which forms a sheath for them the perimysiuin. 

 In some a nucleus may be found, in others none, because the line of section has not been 

 through the situation of the nucleus in the fibre. The variable size of the areas, and the 

 absence of a nucleus in some of them, enable the observer to distinguish easily between the 

 cut ends of non-striped muscular fibres and the mosaic formed by the ends of a number of 

 columnar epithelium cells turned towards the observer, all of which are of the same size, and 

 each one is nucleated. Observe the cement-substance between the fibres. This is best seen 

 when the illumination is slightly diminished by turning off a little of the light with the 

 mirror. Observe also that the fibres are arranged in groups or bundles, surrounded and 

 separated from each other by connective-tissue septa, which are continuous throughout the 

 perimysium. This is continuous with the cement or endomysium, which lies within the bundles 

 between the muscle-cells. {Indicate tlie divided fibres in PI. VII., Fig. 3.) 



CEMENT-SUBSTANCE OF NON-STRIPED MUSCLE. 



PREPARATION. Kill a rabbit, and wash out a piece of the small intestine with distilled 

 water. Fill the intestine with a half per cent, solution of nitrate of silver, and place the 

 distended intestine for ten minutes in a quarter per cent, solution of nitrate of silver. 

 Owing to the difference of concentration of the fluids on the two sides of the gut, diffusion of 

 the silver takes place and so complete saturation of the tissues is obtained. Wash away the 

 silver in ordinary water and expose the gut in alcohol to a strong light. After it has become 

 brown, with a pair of forceps tear off a thin lamina of the outer longitudinal muscular wall of 

 the gut ; steep it in water and float it on to a slide and mount it in Farrant's solution. Another 

 strip may be stained with logwood solution and mounted in dammar, if it be desired to reveal the 

 nuclei of the muscle-cells. Another method of obtaining the outer layer of the muscular coat 

 is to place a small piece of the gut with its external surface next the glass slide ; and then 

 with a knife to scrape away layer after layer from within outwards until only the longitudinal 

 and the serous coats remain. 



EXAMINATION (H). Observe a large number of fine black lines disposed for the most 

 part longitudinally. When carefully traced they are seen to bound narrow fusiform spaces or 

 areas. These silver lines indicate the existence of a cement-substance which holds the fibres 

 together. Lying between the fibres are elongated channels with bulgings upon them, and 

 lined by sinuous epithelium. These are the silvered lymphatics, i.e. lacteals. We shall 

 use this preparation for the study of the general characters of lymphatics. (Indicate the silver 

 lines in PI. VII., Fig. 4.) 



