Pavlov investigated the gastric function of dogs , and later children , by externalizing a salivary gland so he could collect , measure , and analyze the saliva and what response it had to food under different conditions .
In the 1890s , Pavlov was investigating the gastric function of dogs by externalizing a salivary gland so he could collect , measure , and analyze the saliva and what response it had to food under different conditions .