Abstract: Medical specimens suspected of containing harmful microorganisms are diluted in saline solution and the dilution so formed is vacuum loaded into a cuvette or card containing viewing walls having dried selective culture media therein. The dilution rehydrates the culture media, each of which is selective in the sense that its optical characteristics will change when the organism to which it is specific metabolizes within it. A plurality of the cards are loaded into a tray, and the tray is placed on a rotatable carrousel of a card holder unit along with other trays. The carrousel is indexed at periodic intervals, and each time that it is indexed a different tray moves to a reading position facing a card reader unit. The carrousel has a center stack from which heated air is discharged such that it passes along both major surface areas of the cards in the tray, thus maintaining the cards at a temperature suitable for incubating microorganisms in them.

Abstract: Medical specimens suspected of containing certain microorganisms are introduced into cards containing wells having culture media therein. A reduction in the light transmitting characteristics of any well indicates the presence of a microorganism. Each well is examined at periodic intervals by projecting a light through it. This light is monitored by a plurality of detectors located beyond, but nevertheless, in alignment with the well, and each detector provides a signal which is proportional to the intensity of the light cast upon it. If a detector registers an unduly large decrease in light transmission, whereas others associated with the same emitter do not, this probably indicates the presence of a bubble in the well, and the unduly large decrease is ignored. This enables the machine to look around bubbles. Adjustments are made for the change in light transmission caused by distortion of the flexible walls at the ends of the wells.