Abstract: In an apparatus for delivering selectable amounts of dust-laden gas, the base structure thereof includes support means having a substantially horizontal and circular recess in which is rotatably supported a circular disk having a plurality of transverse openings defining a circle coaxial with the disk. A cover partially covers the disk and has a dust container mounted thereon for selective communication with the transverse openings in the disk. The dust container and the circular recess define a substantially airtight chamber. A pair of coaxial openings are provided through the cover and support means for successive alignment with the transverse openings as the disk rotates and are in communication with a source of pressurized gas, whereby pressurized gas can be directed through a dust-laden transverse opening which is aligned with the coaxial openings.

Abstract: An animal inhalation exposure system includes a rectangular exposure chamber, a test atmosphere source communicating with one internal chamber corner through an inlet conduit, and a vacuum source communicating with the diagonally opposite internal chamber corner through an outlet conduit. The said conduits are oriented so that the test atmosphere flows diagonally downwardly through the chamber, the portions of the chamber walls adjacent the inlet and outlet conduits, respectively, facilitating uniform and non-turbulent divergence and convergence of the test atmosphere. Test animal cages with horizontal excreta pans are preferably stacked in the chamber in offset horizontal tiers which define a plane substantially normal to the test atmosphere flow. A holding chamber shares a common wall with the exposure chamber and at least one closable opening is provided in the common wall for transfer of test animals between the chambers.

Abstract: There is disclosed a metering device for metering finely divided material which is capable of handling both free-flowing powders and non-free-flowing powders. The device comprises an upright mixing chamber or reservoir having an axially-disposed stirrer therein. Adjacent thereto is a motor-driven shaft having a metering disc attached thereto with a portion extending into the mixing chamber. The motor-driven axial shaft of the metering disc is connected to the axial shaft of the stirrer by a gear train. Each shaft has replaceable gears attached thereto, adapted to mesh with an idler gear. The idler gear is mounted on an adjustable arm so that the position thereof can be changed when one or both of the replaceable gears is replaced by a gear of different size. In one form of the invention, the stirrer comprises radially-disposed arms projecting from the rotatable shaft, each arm of which is angularly displaced with reference to the arm above or below it and is curved away from the direction of rotation.

Abstract: Novel instantaneously emptiable animal food tray, particularly adapted to be mounted externally of but between two juxtaposed and longitudinally facing animal cages, is disclosed. The tray comprises a bottom which is angled downwardly from a central longitudinal apex to its side edges, vertically extending members at the ends of the tray, and handle means for manipulating the tray into and out of the space between the juxtaposed cages.