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A study of 3535 consecutive autopsied patients over 65 years of age showed that 1,149 patients (32.5%) had one or more cancers. Males were affected by cancer nearly twice as frequently as females in this elderly population (40.3% vs. 23.9%). There were more incidental neoplasms as age advanced. Among the common cancers, the most frequent incidental cancers were those of the prostate gland, kidney, and colon. Cancer tended to metastasize less frequently in the elderly. Several possibilities have been proposed to explain the paucity of metastases in later life.

Isolation of the avian embryo from its normal food material is an essential step in a fundamental study of embryonic nutrition. With present methods, however, it has not been possible to grow embryos in culture for much longer than one day. In 1932 Waddington described methods of growing explanted embryos on serum clots. Several years later Spratt (1947, 1952) devised simplified media for embryos cultured on agar with which he studied various aspects of morphogenesis and carbohydrate needs of the young embryo. New (1955) has recently reported another technique for growing explanted embryos which allows development to proceed to about 60 hours, 40 hours of which are in vitro.

The effects of various dielectric rod cross-sectional profiles on helix velocity dispersion are compared in conjunction with their impact on tube operation. Using these techniques, an 8 to 18 GHz low noise TWT demonstrating excellent gain flatness, good overdrive and harmonic separation has been developed. Detailed design and performance data for this TWT is presented. Electrical and mechanical considerations affecting the use of radial backwall vanes are also detailed. Major design details and performance capabilities of a 1 kW, 2 to 7 GHz, high power pulse TWT are presented asan example of the use of radial vane loading.

SummaryCells are liberated rapidly from minced pectoral muscles of 14-day chick embryos by treatment with a crystalline protease from S. griseus marketed under the name of Pronase. The treatment is carried out in a physiological salt solution. The dissociated cells grow in a standard tissue culture medium and fibroblast type cells predominate in the cultures.

A curved screen placed across a two-dimensional channel causes the streamlines to be deflected on passing through because of the variation in pressure drop across the section and the refraction effect at the screen. Uniform flows far upstream and far downstream are required by the boundary conditions. An analytical description is based on the separation of the field into two regions distant from the screen in which viscosity and molecular diffusion are negligible, plus a thin layer along the screen in which energy loss and streamline deflexion are concentrated. These are described by empirical relationships. For linear velocity and density distribution upstream of the screen, equations can be simplified so that algebraic relationships between the variables at the screen surface are obtained. These have been solved numerically for the shape of screen required to produce a specified velocity distribution. An approximate solution is also obtained for general velocity profiles and the screen shape which produces uniform shear is derived. Experimental verification of the analysis is obtained from measurements of the velocity and temperature distributions downstream of the derived screen shapes mounted in a wind tunnel 45.6 cm square. It is also shown that the boundary layers along a tunnel wall are accelerated or retarded by the screen depending on the loss coefficient. This effect is evident in all observations. The case of homogeneous fluid is described by a simplified version of the analysis and several examples of velocity distributions are produced. These are verified by experiment and compared with those predicted by Elder (1959).