recruiting effort are abnormally low. Unemployment is determined by the rate at which workers lose jobs and the rate at which the unemployed find jobs. I develop a model of fluctuations with a matching friction and sticky wages. The incorporation of wage stickiness makes employment realistically sensitive

developed here explains 1) the benefits of debt in reducing agency costs of free cash flows, 2) how debt can substitute for dividends, 3) why “diversification ” programs are more likely to generate losses than takeovers or expansion in the same line of business or liquidation-motivated takeovers, 4) why

compute the complex function postulated to underlie pretend play. This model also reveals pretense as an early manifestation of the ability to understand mental states. Aspects of later preschool development, both normal and abnormal, are discussed in the light of the new model. This

A case of underdevelopment of the caudal vena cava was observed in an European bison, Bison bonasus (Linnaeus, 1758) aged 49 days, anaesthetized and bled until death because of congenital blindness. The animal had an inbreeding coefficient of 0.389. The abdominal part of this vein was not connected with its thoracic part but was continued as the right azygos vein. Other findings included increased mass of the spleen, its partial division into lobes, and its shifting to the visceral surface of the rumen which was also deformed. The observed abnor malities are related by the authors to a high grade of homozygosity of the animal.

the cultural, social, and physical aspects of an organism's environment. We show the applicability of this view to the understanding of the development of normal and abnormal behavioral and psychological phenotypes through illustrations from the existing animal and human literature. Finally, we discuss

in Megf7-deficient mice

Normally, mice have two populations of lymphocytes; one is long-lived thymus dependent, recirculates, occupies the paracortical region of lymph nodes, bears 0-antigen, and participates in cell-mediated immunity; the other is short-lived, tends to be sessile, occupies the primary follicles of lymph nodes, and can be induced to secrete humoral antibody (1). Both cell types arise from hematopoietic precursors: fetal liver or bone marrow (1, 2). In the absence of a thymus, the normal, rapid differentiation of the long-lived recirculating lymphocyte fails to take place (3). Presumably the thymic epithelial cells induce this normal differentiation (4). Whether this induction requires cell-to-cell contact or whether some other mechanism is involved is still debatable. Mice homozygous for the mutation nude (5) lack thymocytes (6) and thymus-derived cells (7-9) and thus may have a defect of either the hematopoietic precursors of thymocytes or of thymic epithelium. This paper reports studies designed to distinguish between these two major possibilities.

A b s t r a c t Developmental abnormalities of the cerebral venous system occur due to stopped development of the venous system and continuing primitive embryonal veins draining into an abnormal draining vein. Association with occult vascular malformations was detected in patients

Autism is a serious psychological disorder with onset in early childhood. Autistic children show minimal emotional ttachment, absent or abnormal speech, retarded IQ, ritualistic behaviors, ag-gression, and self-injury. The prognosis i very poor, and medical therapies have not proven effective

development, whereas inoculation of CD25- T cells even at a larger dose does not; and furthermore, (c) similar autoimmune diseases can be produced in adult athymic nu/nu mice by inoculating either spleen cell suspensions from 3-d-old euthymic nu/+ mice or CD25 + cell-depleted spleen cell suspensions from