The feline sense of smell is enhanced by a structure in its mouth known as organ.

The given blank can be filled with Jacobson's.

Explanation:

The vomeronasal organ, also known as the Jacobson's organ, refers to an organ of chemoreception, which is a component of the olfactory system of reptiles, amphibians, and mammals. However, it is not witnessed in all the tetrapod groups. It is a sensory cell patch found inside the main nasal passage, which determines heavy moisture-originated odor particles.  

Airborne smells, in comparison, are determined by the olfactory sensory cells situated in the prime nasal chambers. Some mammal groups also exhibit a behavior called flehman response, in which the animal facilitates the exposure of the vomeronasal organ to a pheromone or scent by curling the upper lip and opening the mouth at the time of inhalation.  

In completely developed turtles, crocodilians, cetaceans, birds, and various advanced primates, this composition is not found or is substantially underdeveloped.