Innervation of Crustacean Muscles

Abstract

THE physiology of the striated muscle of Crustacea is known to differ in several respects from that of the vertebrates ; as, for example, in the peripheral location of the inhibitory process, and the presence of separate motor fibres for slow and fast contractions. The interpretation of these peculiar properties requires a knowledge of the histology of the neuromuscular system, in order to compare and contrast it with the mode of innervation of vertebrate muscle. Van Harraveld¹ has put forward the view that each muscle fibre in the crustacean receives a great many endings from each of the different types of nerve fibre, motor and inhibitory, so that it is surrounded by a dense feltwork of axons, and has forty or more nerve endings on its surface. This view is reminiscent of that of Bethe² and Tonner³, both of whom used a methylene blue staining method to demonstrate an extensive network of nerve axons in crustacean muscle. Unlike van Harraveld, however, they derived this network from a “sub-epithelial nerve plexus” and not directly from the central nervous system. On the other hand, D'Ancona⁴, working in Cajal's laboratory, gave a very different histological picture of the peripheral nervous system; he could only demonstrate one or two nerve endings on each nerve fibre, and no nerve network.