By daily subcutaneous injections of morphine a conditioned salivary reflex was established in dogs (confirming Collins and Tatum). This conditioned secretion was a component of the nausea induced in the dogs under the conditions of the experiment. It was found that the conditioned reflex studied is not fully integrated when it first appears, but develops gradually, the curve of development being S-shaped. By stopping the injections of morphine this reflex could be abolished, and by resuming the injections, reestablished. The establishment of the reflex is hindered by starvation. The injections of morphine cause an unconditioned secretion of saliva, the volume collected depending upon the volume of the conditioned secretion of saliva that preceded the injection.