Polyplax alaskensis was first described by H. E. Ewing (1927, Proc. Ent. Soc. Wash., 29 : 118-121) from a single male taken from a mouse, Microtus sp., in Alaska. No subsequent collecting records of this species have been found in the literature. During the summer of 1948 a large series of individuals of both sexes was secured from mice, Microtus o. operarius (Nelson), collected on the Seward Peninsula by the writer. Since the original description is brief and unfigured, I am including here a further description of the species based on the numerous specimens now at hand. Acknowledgments are made to J. C. Bequaert of the Museum of Comparative Zoology and to Floyd G. Werner of the Harvard Biological Laboratories for aid and advice. I am also very grateful to C. F. W. Muesebeck of the Bureau of Entomology and Plant Quarantine, U. S. Department of Agriculture, for corroborating the identification by comparing a specimen from my series with the type. Female (Fig. 1, A). Length 1. 2-1.4 mm. Head almost as broad as long and generally similar to that of spinulosa ; first antenna joint much longer than the others and set close to the anterior margin. Thorax dorsally similar to that of spinulosa ; ventrally, the sternal plate is longer than it is broad; the anterior lateral margins are nearly parallel ; the posterior lateral margins are concave and slope to a blunt point ; the legs, of usual form, are of increasing size posteriorly. Pleural plates : (Fig. 2, B) first pleurite elongate, faintly if at all chitinized medially and usually with three
The theory for the diffusion-controlled growth of ferrite in steels that also contain substitutional solutes is fraught with difficulties when it comes to transformation at large supersaturations, where the bulk compositions of the ferrite and austenite do not differ much, but where local-equilibrium is nevertheless maintained at the transformation front. This requires the existence of a narrow variation in substitutional solute content in the austenite at the interface (so-called ‘concentration spike’) so narrow that it has no physical meaning. Drawing on the theory for spinodal reactions, it is demonstrated here that there is a substantial penalty associated with the creation of such sharp changes in composition. Therefore, the spikes would never occur in practice. The actual distribution of solute would be over distances orders of magnitude larger than currently calculated, leading to slower growth rates than are predicted currently. The consequences of this conclusion place doubt both on the transition from local to paraequilibrium, and whether the latter state exists at all for reconstructive transformations.
With reference to sixteen cases of polyarteritis nodosa (seven dogs, two cats, two goats, three pigs, two cattle), current views regarding classification, aetiology and pathogenesis of this disease are discussed. Polyartertis nodosa is not a disease entity, but rather a symptom that may be associated with various forms of disease and may vary in pathogenesis. The clinical picture depends upon the localisation of the vasculitis. Toxic agents and various viruses may be directly responsible for the vascular lesions. In addition, genetic, autoimmune and allergic factors may be implicated. The immunological pathogenesis is illustrated with reference to the serum sickness model.
