Depending on the breed, your dog has between 125 million to 300 million scent glands — compared to only five million for humans. and the part of your dog’s brain that controls smell is forty times larger than yours — that’s true, although the canine brain is way smaller than the human, relative to size. A human’s brain is about 1/40th of their body weight whereas a dog’s brain is simply 1/125th. Don’t feel too smug, though — an ant’s brain is 1/7th its body weight.