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On the Nature of the Lateral Muscle in Teleostei.
Author(s) -
Shann Edward W.
Publication year - 1914
Publication title -
proceedings of the zoological society of london
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.915
H-Index - 96
eISSN - 1469-7998
pISSN - 0370-2774
DOI - 10.1111/j.1469-7998.1914.tb07040.x
Subject(s) - anatomy , dorsum , biology
Summary.1 The body‐wall of a Teleostean fish is composed on either side of a series of transverse muscles (myomeres) divided from one another by fasciæ of connective‐tissue (myocommata). For practical purposes these may be regarded collectively as forming a single lateral muscle. 2 The lateral muscle is composed of a single layer, which varies considerably in thickness in different parts of the body. 3 In its primary condition, such as obtains in the caudal region, it is divided into two symmetrical longitudinal moieties, which are separated by a horizontal septum passing from beneath the lateral line to the vertebral column. 4 The dorsal moiety is marked externally by a series of backwardly directed >‐shaped bands. By joining the apices of these >'s an imaginary line is formed dividing the dorsal moiety into a (dorsal) mesio‐dorsal portion and a (ventral) latero‐dorsal portion. In the mesio‐dorsal portion the muscle‐fibres run from above anteriorly to below posteriorly; in the latero‐dorsal portion they take the opposite inclination. Internally the mesio‐dorsal portion is recognised as a series of incomplete hollow pyramids, or cones, whose apices are directed posteriorly; while the latero‐dorsal portion is composed of a series of complete hollow pyramids, or cones, whose apices are directed forwards. The ventral moiety is likewise divided into a (dorsal) lateroventral portion and a (ventral) mesio‐ventral portion. The fibres of the latter, at first oblique, as they approach the middle line become straight, and resemble a rectus. 5 The above divisions of the dorsal and ventral moieties suffice for descriptive purposes; but, pending further evidence, they must be regarded as essentially empirical in nature. 6 Small cylindrical longitudinal muscles are frequently cut off from the mesio‐dorsal portion, along the mid‐dorsal line in the interspaces of the dorsal fins. These are the supracarinales of Owen. Similar muscles are frequently cut off from the mesio‐ventral portion along the mid‐ventral line. These are the infracarinales of Owen. 7 A small muscle, whose fibres are usually distinguished by their red colour, is cut off from the latero‐dorsal portion and occupies the slope of the furrow in which the lateral nerve is situated. A corresponding muscle is cut off from the latero‐ventral portion immediately below the lateral line.