Notochordal and elastic components of the axial skeleton of fishes and their functions in locomotion

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Abstract
Structural details of the notochord and elastic longitudinal ligaments (dorsal and ventral) of fish are presented with discussions on their possible contribution to the speed, power and modes of swimming by conferring an automatic spring‐like resilience to the vertebral axis as a whole. The notochord is also believed to function as a series of ring‐like hinges placed intervertebrally which dictates that the centra must be biconcave (amphicoelous) to support and house them. Examination of about 100 species shows that, whilst the dorsal ligament is always present, the ventral is found in primitive teleosts only. The phylogenetic significance of this in relation to the different efferent branchial systems will be submitted (with diagrammatic recording of dissections) for publication in the near future. The dorsal and ventral ligaments are suitably situated to assist the circulation of lymph and blood respectively in the small lateral vessels associated with the main longitudinal one of the appropriate system. Experimental work is required to test the hypotheses presented.