Pair Of Claws Research Articles

DEVELOPMENT OF THE DIMORPHIC CLAW CLOSER MUSCLES OF THE LOBSTER,HOMARUS AMERICANUS:II. DISTRIBUTION OF MUSCLE FIBER TYPES IN LARVAL FORMS

1. The closer muscles of the paired claws (chelipeds) of lobsters were characterized according to the distribution of short, long and intermediate sarcomere muscle fibers during the three larval stages.2. Unlike the adult lobster, where the claws and closer muscles are asymmetrical, the claws and closer muscles of the larval stages are symmetrical.3. In the first and second larval stages, the closer muscle is composed of over 50% intermediate sarcomere fibers, 30-40% short sarcomere fibers and less than 10% long sarcomere fibers.4. By the late third stage the long sarcomere fibers have increased to a maximum of 40% with a corresponding decrease in number of intermediate fibers.5. Thus, at the end of the last larval stage, the closer muscles are symmetrical, with muscle fibers about equally distributed among short, intermediate and long sarcomere fiber types.6. The data are consistent with the hypothesis that intermediate fibers are transformed into long sarcomere fibers but not into short sarcomere fibers.

The Anatomy of the Tarsi of Schistocerca gregaria Forsk�l

The tarsus of S. gregaria is divided into three units (here called segments) and an arolium set between a pair of claws. The first segment bears three pairs of pulvilli in the fore and middle legs, and one pair and two single pulvilli in the hind legs. Segment two bears a pair of pulvilli, segment three one long pulvillus and the arolium a similar pad on the undersurface. The outer layers of the arolium pad differ from those of the pulvilli in possibly lacking an epicuticle and in having a layer of cuticle which, unlike the corresponding layer in the pulvilli, does not stain with protein stains. The claws and dorsal surfaces bear trichoid sensilla, basiconic sensilla and campaniform sensilla. Smaller basiconic sensilla and canal sensilla occur on the proximal part of the pulvilli, and basiconic sensilla on the arolium undersurface. Internally the cuticle is modified in the arolium and pulvilli so that rods of probably chitin and resilin are formed. This would impart flexibility to the undersurfaces whilst retaining some degree of rigidity which might prevent damage to the small and delicate sense organs on the pulvilli. The tip of the arolium is specialised for adhesion, and there are two large neurones internally which could conceivably monitor attachment or detachment of the tip. There are chordotonal organs in segment three, and several other large neurones throughout the tarsus, some of which are associated with the slings of tissue holding the apodeme in a ventral position. Gland cells occurring in the dorsal epidermis of the adult mature male are also briefly described.

OPTICO-CILIARY NEUROTOMY, WITH EXHIBITION OF SCISSORS.Read in the Section on Ophthalmology, at the Forty-fifth Annual Meeting of the American Medical Association held at San Francisco, June 5-8, 1894.

I wish to present for the consideration of this Society a modification of my ablation scissors: Scissors for performing optico-ciliary neurotomy. The original instrument was described in the Archives of Ophthalmology , Vol. xvi, No. 1. It consisted of two curved scissors placed parallel so as to enable one to cut a section of the optic and ciliary nerves without cutting any of the ocular muscles. The modifications consist in the addition of a pair of claws between the two scissors to insure the removal of the cut section of the nerves. Any one who has to perform the operation of removing a section of the nerves by first dividing the internal rectus and then uniting the muscle with sutures, as is done by some operators, has found it quite a formidable operation if it has to be done without the aid of trained assistants. These operators, I think, will find