What does it mean that people reach the navel and horses reach the lungs?

The navel leads to the lungs, which is a visual statement and is often used to describe the gap between people and animals. Specifically, this sentence means that there are insurmountable differences between human heart and animal instinct in some aspects. Man's reaching the navel refers to the deep heart of man, which shows that human beings have more complicated emotional, ideological and spiritual activities. From horses to lungs, it emphasizes the instinct, physiological needs and simple reaction ability of animals. There are essential differences between them, which determine that the behavior patterns and cognitive styles of human beings and animals will be different.