Roof of the Mouth
It's the Jacobsons Organ
The Jacobson's Organ - is a sensitive 'pit' located in the roof of a reptiles mouth. When a reptile flicks out it's tongue, tiny scent particles stick to it - and are drawn back into the mouth. the tips of the tongue are placed into the Jacobson's Organ, and the reptile 'analyses' the scent. This organ is so sensitive - it can even distinguish if the scent on one side of the forked tongue is stronger than the other side !
Rattlesnakes specialize in small mammals. They them using sensory organ that detect infrared, or radiant heat, coming off of mammals. A field mouse is a small mammal and would definitely be eaten by a rattlesnake that could catch it.
kidney, skin,
With there tongue! They flick their tongue in and out of their mouth to sence the air when the tongue is out it picks up scents and when it is flicked back into the mouth it rubs against the jacobsons organ which converts the sences and allows the snake to understand its surroundings
All mammals use lungs to breath.
All mammals, including humans, breathe using their lungs.
hypothalamus
lateral line organ
In mammals and fish it is lungs
circulatory system
Liver