MYOLOGY OF FISHES. 203 



segments, corresponding in number with the vertebrae. Each 

 lateral flake (myocomma, fig. 131, a, b, c) 1 is attached by its inner 

 border to the osseous and fibrous parts of the corresponding 

 vertically extended segment of the endoskeleton, by its outer 

 border to the skin, and by its fore and hind surfaces to an aponeu- 

 rotic septum common to it and the contiguous myocommas. The 

 gelatinous tissue of these septa is dissolved by boiling, and the 

 muscular segments or flakes are then easily separated, as we find 

 in carving a fish at table. The vegetative similarity of the myo- 

 cornmas of the trunk has led to their being described as parts of 

 one f great side-muscle,' extending from the occiput and scapular 

 arch to the bases of the caudal fin-rays. The modifications of the 

 cranial vertebrae impress corresponding changes on their muscular 

 segments, and special names have been conveniently applied to 

 their constituent, and in fact often separated and independently 

 acting, fasciculi. 



The fibres of each myocomnia of the trunk run straight and 

 nearly horizontally from one septum to the next ; but they are 

 peculiarly grouped, so as usually to form semi-conical masses, of 

 which the upper, a, and lower, 5, have their apices turned back- 

 ward ; whilst a middle cone, c, formed by the contiguous parts of 

 the preceding, has its apex directed forward ; this fits into the 

 interspace between the antecedent upper and lower cones, the 

 apices of which reciprocally enter the depressions in the succeed- 

 ing segment, whereby all the segments are firmly locked together, 

 their general direction being from without obliquely inward and 

 backward, and their peripheral borders describing the zig-zag- 

 course represented in fig. 131, in which one myocomma is repre- 

 sented partly detached, and others quite removed from the side of 

 the abdomen. Thus, guided by the fundamental segmental type 

 of the vertebrate structure, we come to recognise the ( grand 

 muscle laterale,' of Cuvier, as a group of essentially distinct 

 vertical masses or segments. A superficial view of these seg- 

 ments, or an artificial analysis, has led to their being regarded as 

 forming a series of horizontal muscles, extending* lengthwise from 



O O CJ 



the head to the tail : the upper portions, , of the myocommas 

 being grouped together, and described as a dorsal longitudinal 



1 Professor Goodsir proposes (CLXXVIII.) to alter this term to ' myotome,' and to 

 substitute for 'vertebra' or 'osteocomma' (CXLI, 1849, p. 88) the term ' sclerotome,' 

 &c. : but this form of compound has been pre-engaged, for their -special cutting 

 instruments, by the sclerotomists, neurotomists, lithotomists, and other classes of 

 operating surgeons and their instrument-makers. If the itch of change be uncontrol- 

 lable, I would suggest 'osteomere,' ' scleromere,' ' neuromere,' &c. (Gr. ^pos, part 

 instead of Kcfyt/ua, segment. 



