Animal Physiology

Our knowledge of the action of caffeine on the respiratory system has resulted mainly from studies on the effect of the drug on the rate and rhythm of respiration, alveoli and total ventilation of the lungs, and on the volume of gas exchanged between the organism and its environment. Edsall and Means (1), Grabfield and Means (2), Higgins and Means (3), Lohr (4), Schmidt and Harer (5), Smith (6), Fsungming (7).There seems to be a general agreement among these investi- gators that caffeine stimulates the respiratory center resulting in an increase in the rate of respiration and an increase in the oxygen consumption and carbon dioxide elimination. This in- crease in the gaseous exchange may not be entirely due to stimulation of the respiratory center, but to some other factor such as an increase in the basal metabolism.Owing to the fact that practically all of the previous experiments were conducted on mammals, which have the highest developed nervous system of any group of animals, and in order to throw more light on the fundamental effect of the drug on physiological processes, it was thought desirable to study the effect of caffeine on the oxygen consumption of lower organisms.For this purpose it was found advantageous to use young individuals (3 to 4 inches in length) of a fresh water fish, Erimyson sucetta oblongus, Mitchell (identifled by Dr. T. H. Langlois, University Museum, University of Michigan) and bull frog tadpoles, Rana catesbiana. These ani- mals remain rather quiet when not disturbed, thus the error in 1 Contribution from Battle Creek College. 5960 FLOYD J. BRINLEY oxygen consumption due to bodily activity of the animals is reduced to a minimum but not completely eliminated. M