The term pheromone was first designated by Karlson and Lüscher in 1959 as a substance secreted by an animal to the outside of that individual, which was then received by another individual, classically of the same species, and which then elicited some behavioral or developmental response in the latter. They composed the term from the Greek words pherein, which means to bring or to transfer, and hormon, which means to excite. In the usual context, this response in the second individual is of a sexual or of a reproductive physiologic nature, although sometimes the definition might even be extended to include other social responses such as when a dog uses pheromones in urine to mark territory. Classically, pheromones are thought of as being olfactory, but these chemicals may also be received by contact. Pheromones may be present in many different sites in animals, such as in the skin, including some of its glands, saliva, urine, vaginal discharge, and feces.