Abstract: The invention relates to an apparatus for measuring the heart rate and the respiration rate of one or more anesthetized rodent while monitoring and maintaining body temperature of at least one or more anesthetized rodent during diagnostic or surgical procedures. The apparatus includes a printed circuit board having four electrodes, two of which are injection electrodes and two of which are sensor electrodes. The heart rate is monitored through known electrocardiogram techniques, however, the respiration rate is monitored by injecting an electrical current across the chest of the rodent between two of the electrodes to determine impedance of the electrical current across the chest of the rodent. The impedance is carried by a respiration signal that is then graphically displayed to measure and, thus, monitor the respiration rate. The apparatus further includes the ability to maintain and monitor the body temperature of the rodent.