Since handshakes are out of the question, dogs need a way to introduce themselves to one another. Dogs get to know each other by sniffing each other’s butts.  It is the chemical trail from a dog’s anal sacs that create a dog’s signature scent. Why is smell so important to a dog? It is because a dog’s nose is 10,000 to 100,000 times more sensitive than a humans, due to the dog’s large olfactory membrane that holds more than 225 million scent receptors. It only makes sense that their nose would play such a crucial role. Dogs that smell each other’s butts are able to gather valuable information about the other dog. One sniff and a dog can detect the other dog’s diet, gender and emotional state. Amines and acids in the anal sacs are responsible for housing all of this information. A dog can even sense the state of the other dog’s immune system by sniffing his butt. Dr. George Pretti of the Monell Chemical Senses Center in Philadelphia, studied anal secretions from dogs and wild coyotes. A dog’s apocrine gland is what is responsible for the way a dog smells. This sharp odor is also sensed by a dog in what is known as their Jacobson’s organ. This delivers the chemical information about the other dog straight to the dog’s brain. The dog also uses this organ when he sniffs out the scent of pee from dogs who have come before him. And there you have it. Dogs sniff each other’s butts to say hello and get to know each other in a most intricate way.