A restraining tube for small animals (preferably animals with tails) is designed to facilitate physiologic measurements of the animal through an integrated or associated sensor mount. The physiologic sensors include those for the measurement of pulse oximetry and other measurements such as breath rate, heart rate, pulse distention and breath distention, temperature to name a few. A tail engaging sensor mount geometry is provided for a particular pulse oximeter into the back plate of the tube. The immobility of the animal is especially important given the fact that pulse oximetry measurements are extremely susceptible to even the smallest motion artifact.