Abstract: A method and apparatus for continuously monitoring gases exhaled by animals in a laboratory environment for the presence of hepatic bilirubin permits long-term monitoring in which samples are directed into each of a series of sample containers by evacuating each container over a selected time interval while retaining the other containers in a closed position. The gas supply and gas evacuation lines to and from each sample container are simultaneously controlled via a programmer controlled circuit to permit automated sequential filling of the sample containers over a long-term interval. The sample containers are mounted in a wall-mounted cabinet having hinged display shelves for the containers with a common control panel behind the shelves to regulate the sampling and filling operation.