MUSCACE.E. 



[ 444 ] 



MUSCLE. 



black bands, abdomen blackish-brown above, 

 with blackish elongated spots, pale yellow- 

 ish-brown beneath. 



M. carnaria, L. {Sarcophaga, Meigen), 

 the flesh-fly. Antennae feathery ; head 

 golden-yellow in front, eyes reddish ; thorax 

 gray with black longitudinal lines, abdomen 

 black, with four square white spots on each 

 segment, all the body strewed with black 

 hairs. Viviparous, 1-2" long. 



M. Ccssar, L. {Lucilia, Donov.). No spots, 

 abdomen green, with a metallic lustre. 



31. vomitoria, L. ( Calliphora, Donov.), blue- 

 bottle or blow -fly. Head yellowish, golden 

 or white, eyes brown ; thorax black ; abdo- 

 men shining blue with black stripes and 

 long black hairs. 



The larvae are known as gentles. The 

 ova or larvae are deposited upon animal or 

 vegetable substances, mostly in a state of 

 decay, upon which they live. 



Several parts of the species of Musca are 

 of general microscopic interest : — as the 

 proboscis (PL 26. fig. 29) with its two fleshy 

 lobes (c), kept expanded by a beautiful and 

 elastic framework of modified tracheae ; the 

 setae or lancets (6), which are modified 

 maxillae, sometimes rudimentary, with their 

 palpi («) at the base ; the remarkable an- 

 tennae (PI. 26. fig. 20) ; the elegant tarsus 

 (PI. 27. fig. 7 a), with its terminal spine, 

 pulvilli (figs. 7, 8 & 9) and claws; and the 

 rudimentary wings (halteres. Insects, p. 

 358). 



Musca jJumilionis {Chlorops, Meig.) de- 

 posits its eggs in the young wheat-grain, 

 which is consumed and destroyed by the larvae. 



Many other members of allied families of 

 Diptera, commonly known also as flies, are 

 of microscopic interest, on account of their 

 oral setae or lancet-like organs. 



BiBL. Westwood, Introduction, ^'c; Mac- 

 quart, Hist. nat. d. Ins. Dipt. ; Meigen, 

 Syst. Beschr. d. hek. eur. zweifliig. Insect. ; 

 Keller, Gesch. d. gemein. Stubenfliege ; 



MUSCACE^. See Mosses. 



MUSCLE. — Muscular tissue forms the 

 greater portion of the flesh of animals. 



It occurs in two principal forms ; one of 

 which is termed organic, unstriated, or un- 

 striped muscle ; the other, voluntary, striated 

 or striped muscle. 



Unstriated muscle, — This consists of more 

 or less elongated, somewhat spindle-shaped, 

 narrow fibres (p. 62, fig. 34), having the 

 import of cells, and hence often called fibre- 

 cells. They are, however, solid. Each 

 contains an elongated nucleus, brought to 



light by the addition of acetic acid, but ex- 

 hibiting no nucleolus. The fibres are of 

 variable length, from about 1 -580 to 1 -250", 

 and 1-5000 to 1-3500" in diameter. They 

 sometimes exist singly in the midst of areolar 

 tissue ; at others they are united into rounded 

 or flattened bundles, and surrounded by an 

 imperfect kind of sarcolemma, composed of 

 areolar tissue with elastic fibres. 



They occur most abundantly in the hollow 

 viscera; as the stomach, the intestines, the 

 bladder and the uterus ; but they also exist 

 in other situations, as the spleen, trachea 

 and bronchi, the dartos, the arteries, veins, 

 and lymphatics, the prostate gland, fallopian 

 tubes, urethra, villi of the small intestines, 

 the skin, iris, &c. 



Fig. 502. 



Unstriated muscular fibres from the oesophagus of a 

 pig, after treatment with diluted nitric acid. 



Magnified 10 diameters. 



Striated muscle. —The structure of striated 

 is more complex than that of unstriated 

 muscular tissue. It consists of a num- 

 ber of very slender fibres, called fibrillae, 

 connected into bundles, termed primitive 

 bundles or fasciculi, each of which is en- 

 closed in a sheath or sarcolemma. The pri- 

 mitive bundles are again united into second- 

 ary and tertiary bundles, the whole being 

 bound together by a connected mass of 

 areolar and elastic tissue surrounding each 

 of them, and forming the perimysium. This 

 arrangement is best seen in a transverse sec- 

 tion (fig. 503). 



The primitive bundles are from about 1-1 000 

 to 1-200" in diameter, and of a rounded or po- 

 lygonal form (fig. 504). Their surfaces are 

 marked by a number of transverse striae, 

 which forms the most characteristic appear- 

 ance of the tissue. They also exhibit irre- 

 gular longitudinal striae, which are the indi- 



