the intermediate substance is the sarcoplasm. In some muscles, apparently, each fibrilla is surrounded by a considerable amount of sarcoplasm, in which case the fibrillae are easily isolated from one another and can be readily examined. This is the case in the wing muscles of insects.
|Fig. 12.—Transverse section of a||Fig. 13.—Isolated|
|striated muscle fibre.||smooth muscle fibres.|
|n,Nucleus.||Very much contracted.|
|s,Sarcoplasm.||Fibres tapering at each|
|m, Bundle of fibrillate forming||end, with nucleus|
|a muscle column.||centre of cell.|
The nuclei of the fibre are arranged close under the sarcolemma. Each is surrounded by a small quantity of sarcoplasm and in shape is an elongated ellipse. In most cases the muscle fibres do not branch, though in a few instances, such as the superficial muscles of the tongue, branching is found.
Involuntary or Smooth Muscle (figs. 13 and 14).—This form of muscle tissue when separated into its single constituents is seen to consist of fibres possessing a typical long spindle shape. The central part is somewhat swollen and contains an elongated nucleus centrally placed. The ends of the fibres are drawn out and pointed sharply. There is no definite surrounding membrane to each cell. In most of the cells, especially the larger, a distinct longitudinal marking can be seen. This is due to the presence of the fibrils which run the length of the fibre and in all probability are the essential contractile elements.
In most instances the cells are arranged with one another in a tissue to form bundles or sheets of contractile substance. In each bundle or sheet the cells are cemented to one another so that they may all act in unison. The cementing material is apparently of a membranous character and is so arranged that contiguous fibres are only separated by a single layer of membrane. According to some, neighbouring fibres are connected to one another by minute offshoots, and these communications serve to explain the manner in which the contraction is observed to pass from fibre to fibre along a sheet composed of the muscles.
|Fig. 14.—Preparation of Frog’s Bladder showing smooth muscle in situ forming a network.|
Involuntary muscle is the variety of muscle tissue found in the walls of the hollow viscera such as stomach; intestines, ureter, bladder, uterus, &c., and of the respiratory passages, in the middle coats of arteries, in the skin and the muscular trabeculae of the spleen.
The arrangement is very typical, for instance, in the small intestine. Here the muscular coat consists of two layers of muscle. Each is in the form of a sheet which varies greatly in thickness in different animals. In the inner sheet the fibres, which are all parallel to one. another, are disposed with their long axis transverse to the direction of the gut. In the outer layer, the direction of the fibres is at right angles to this. In a. viscus with thick muscle walls the fibres are bound into bundles and the bundles may run in all directions. In some instances the bundles may form branching systems, thus constituting a network, as in the bladder (fig. 14). In other instances, e.g. the villi of the small intestine, the muscle fibres are separate, forming a felt-work with wide meshes.
|Fig. 15.—Cardiac Muscle. Isolated cells.|
Heart Muscle.—The fibres of which the muscular walls of the heart are composed though cross striated are not voluntary, for they are not under the control of the will. Each fibre is an oblong cell possessing distinct transverse and less distinct longitudinal striations (fig. 15). There is no sarcolemma, and the nucleus of each fibre is placed in the centre. The longitudinal striation is due to the presence of fibrillate, each of which is cross striated. These lie parallel to one another in the cell, the sarcoplasm surrounding them being much more abundant in these fibres than is striated muscle. The fibrillae are arranged in rows, and when a transverse section of one of these fibres is examined it is seen that the rows radiate away from the centre of the cell. A further distinctive character of cardiac muscle fibres is that they frequently branch, the branches uniting with others from neighbouring cells. Moreover the ends of the fibres are attached to corresponding faces of other cells, and through these attached faces the fibrillae pass, so that there is an approximation to the formation of a syncytium. (T. G. Br.)
CONNELLITE, a rare mineral species, a hydrous copper chloro-sulphate. Cu15(Cl,OH)4SO16·15H2O, crystallizing in the hexagonal system. It occurs as tufts of very delicate acicular crystals of a fine blue colour, and is associated with other copper minerals of secondary origin, such as cuprite and malachite. Its occurrence in Cornwall was noted by Philip Rashleigh in 1802, and it was first examined chemically by Arthur Connell in 1847. Outside Cornwall it has been found only in Namaqualand in South Africa.
CONNELLSVILLE, a borough of Fayette county, Pennsylvania, U.S.A., on the Youghiogheny river, about 60 m. S.S.E. of Pittsburg. Pop. (1890) 5629; (1900) 7160, including 800 foreign-born; (1910) 12,845. It is served by the Pennsylvania, the Pittsburg and Lake Erie, and the Baltimore & Ohio railways, and by the interurban electric system of the West Penn Railway Co., which has a large power plant near Connellsville. Connellsville is the centre of the Connellsville coke district (in Fayette and Westmoreland counties), which has the largest production in the United States, the output in 1907 (13,089,427 tons) being 32.1% of that of the whole country. Connellsville coke is the standard grade. What is called the Lower Connellsville coke region lies in Fayette county S.W. of the Connellsville district. It is richest near Uniontown, and in 1907 produced 6,310,900 tons of coke, making it second only to Connellsville. The so-called Upper Connellsville (or Latrobe) district, near Latrobe, produced in 1907, 1,030,260 tons of coke. The combined output of these three districts in 1907 was 50.1 % of the total of the entire country. The borough of Connellsville has various manufactures including iron, tin plate, automobiles and various kinds of machinery; and a state hospital for the treatment of persons injured in mines is located here. Connellsville was first settled in 1770, was laid out as a town by Zachariah Connell, in whose honour it was named, in 1793, and was incorporated in 1806. The borough of New Haven (pop. in 1900, 1532) was annexed to Connellsville after the census enumeration of 1900.
CONNEMARA, a wild and picturesque district in the west of Co. Galway, Ireland. (See Galway.)
CONNERSVILLE, a city and the county-seat of Fayette county, Indiana, U.S.A., situated on White Water river, in the east central part of the state, about 50 m. E. by S. of Indianapolis. Pop. (1900) 6836; (1910) 7738. It is served by the Cincinnati, Hamilton & Dayton, the Cleveland, Cincinnati, Chicago & St