CRUSTACEAN BLOOD COAGULATION AS STUDIED IN THE ARTHROSTRACA

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Abstract
1. This communication, histological throughout, is virtually a continuation and extension of a previous publication by W. B. Hardy on crustacean blood corpuscles. The explosive cells discovered by Hardy in the crayfish have been studied in films of isopod blood, and have been found to discharge into the immediately surrounding plasma a material which either itself coagulates or there induces coagulation in the portions of plasma reached by it. In this way a little localised island of coagulation is formed around each exploded corpuscle.2. These islands, once formed, are fixed structures, with a definite boundary, which has no tendency to become diffuse or to spread outwards. There is thus a limit to the range of action of the explosive corpuscles, and there is no evidence that, as Hardy suggested, they yield a ferment which causes the plasma as a whole to coagulate.3. On first formation, these localised coagula are plastic structures, which can be modified in shape by movements of the surrounding fluid. They are likewise sticky, and tend to adhere to or entangle any cells with which they come in contact. They soon set and harden, however. In a film that has been kept at rest their usual form is circular.4. The actual formation of these coagula in situ at a wound may be watched in the amphipod Gammarus, and the part which they play in the natural arrest of hæmorrhage thus studied. They help to stop the bleeding by forming an adherent bunch of globules or botryoidal mass at the site of injury. To these globules issuing blood cells tend to adhere, thus further clogging up the paths by which the blood escapes.5. The birth of one of these globules is accompanied by a considerable output of kinetic energy, the explosion consisting not merely in a shedding‐out of material from the corpuscle, but in an actual rending and breaking apart of the immediately surrounding clot. This process suggests an analogy with Macdonald's hypothesis regarding the cause of muscle contraction.6. The part played by these localised coagula must not be taken in the meantime to supersede or dispose of the cell‐agglutination hypothesis put forward by other authors as the cause of the first coagulation in crustacean blood. According to the view here taken, the phenomenon exists alongside of and ultimately associated with cell agglutination as a contributing factor in arrest of hæmorrhage.7. A second coagulation of isopod blood, this time involving the whole plasma indiscriminately, may be made out in addition to the afore‐mentioned localised coagulation. There is no histological evidence to associate this second coagulation with the disintegration of any one particular element of the blood more than another.The expenses of this research were defrayed by a grant from the Carnegie Trust.

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