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  • Author or Editor: C.A.G. Wiersma x
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Abstract

The innervation as described for the crayfishes has been confirmed in the lobster and it has been possible to extend the innervation scheme to more muscles. (Fig. 1). The innervation of the main and accessory flexors are described here for the first time in an Astacuran. As expected the main flexor is innervated by 4 motor fibers and 1 inhibitory one, the accessory flexor by 1 motor and 1 inhibitory fiber. The latter was shown to be a branch of the inhibitor which supplies the extensor and the bender. It has not been possible to show that the inhibitory fiber of the main flexor is likewise a branch from one of the other inhibitors. Though this was the case in all other species thus far fully investigated. The question arises therefore, whether a 4th inhibitor is present in the Astacura, or whether one of the inhibitors branches in the proximal part of the leg, before the ischiopodite. It is not possible to decide this question. It seems unlikely that the stretcher inhibitor would branch so early, as this fiber runs in the small bundle with the main flexor axons. Again, the branch to the accessory flexor of the "third" inhibitor may be taken as an indication that the latter is not involved. There remains the opener inhibitor, which in Panulirus does inhibit the main flexor, but which there does not cross to the thicker bundle. In order to decide whether 3 or 4 separate inhibitors are present it would be necessary to use the whole leg, a procedure which would kill the animal, and would even then, because of the inclusion of the place of autotomy, be difficult to perform. Because of the scarcity of the material this type of experiment was not tried.

In: Archives Néerlandaises de Zoologie
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Abstract

The different thoracic legs of the lobster Homarus vulgaris have been compared with regard to the contractions caused in the closer muscles on one and more impulses in the "fast" nerve fiber. It was found that small twitches occurred in the fresh preparations especially in the second and third legs; that the cutter claw, the fourth and fifth leg showed sometimes a very small contraction on a single shock, but that in the crusher claw more than two closely spaced impulses are necessary before a visible contraction occurs. Two closely spaced impulses in the second, third and fourth leg lead to a stronger twitch, which increases considerably in strength on further impulses. In the cutter claw two such impulses lead to a very strong twitch, which increases but little with a greater number of impulses. Muscle action potentials lead from the muscle with external leads

In: Archives Néerlandaises de Zoologie