NON-STRIPED MUSCLE. 



461 



contain one or more nucleoli. It is brought into view by the action of dilute acetic acid, or by 

 staining reagents. The mass of the cell appears more or less homogeneous, [and is surrounded 

 by a thin elastic envelope]. In some places it shows longitudinal fibrillation. [Method. This 

 fibrillation is revealed more distinctly thus : Place the mesentery of a newt (Klein) or the 

 bladder of the salamandra maculata (Flemming) in a 5 per cent, solution of ammonium 

 chromate, and afterwards stain it with picro-carmine. Each cell consists of a thin elastic 

 sheath (sarcolemma of Krause) enclosing a bundle of fibrils (F) which run in a longitudinal 

 direction within the fibre (fig. 313). They are continuous at the poles of the nucleus with the 

 plexus of fibrils which lies within the nucleus, and, according to Klein, they are the contractile 



{>art, and when they contract the sheath becomes shrivelled transversely and exhibits what looks 

 ike thickenings (S). These fibrils have been observed by Flemming in the cells while living. 

 Sometimes the cells are branched, while in the frog's bladder they are triradiate. 



[Arrangement. Sometimes the fibres occur singly, but usually they are arranged in groups, 

 forming lamellse, sheets, or bundles, or in a plexiform manner, the bundles being surrounded by 

 connective-tissue.] A very delicate elastic cement-substance unites the individual cells to each 

 other. [This cement may be demonstrated by the action of nitrate of silver. In transverse 

 section (fig. 312, 11) they appear oval or polygonal, with the delicate homogeneous cement 

 between them ; but, as the fibres are cut at various levels, the areas are unequal in size, and all 

 of them, of course, are not divided at the position of the nucleus. ] 



They vary in length from y^ to -%%-$ of an inch ; those in the middle coat of the arteries 

 are short, while they are long in the intestinal tract, and- especially in the pregnant uterus. 

 According to Engelmann, the separation of the smooth muscular substance into its individual 

 spindle-like elements is a post-mortem change of the tissue. Sometimes transverse thickenings 

 are seen, which are not due to transverse striation, but to a partial contraction. Occasionally 

 they have a tendinous insertion. 



Blood- Vessels. Non-striped muscle is richly supplied with blood-vessels, and the capillaries 



Fig. 312. Fig. 313. Fig. 314. 



Fig. 312. Smooth muscular fibres (10) ; (11) transverse section. Fig. 313. Smooth mus- 

 cular fibre from the mesentery of a newt (ammonium chromate). N, nucleus ; F, fibrils ; 

 S, markings in the sheath. Fig. 314. Termination of nerve in non-striped muscle. 



form elongated meshes between the fibres, [although it is not so vascular as striped muscle]. 

 Lymphatics also occur between the fibres. 



Motor Nerves. According to J. Arnold, they consist of medullated and non-medullated 

 fibres [derived from the sympathetic system] which form a plexus ground plexus partly pro- 

 vided with ganglionic cells, and lying in the connective-tissue of the perimysium. [The fibres 

 are surrounded with an endothelial sheath.] Small branches [composed of bundles of fibrils] 

 are given off from this plexus, forming the intermediary plexus with angular nuclei at the noda) 

 points. It lies either immediately upon the musculature or in the connective-tissue between 

 the individual bundles. From the intermediary plexus, the finest fibrillar (0*3 to 0"5/x) pass 

 off, either singly or in groups, and reunite to form the intermuscular plexus (fig. 314, d), which 

 lies in the cement substance between the muscle-cells, to end, according to Frankenhauser, in 

 the nucleoli of the nucleus, or in the neighbourhood of the nucleus (Lustig). According to J. 

 Arnold, the fibrils traverse the fibre and the nucleus, so that the fibres appear to be strung upon 

 a fibril passing through their nuclei. According to Lowit, the fibrils reach only the interstitial 



