Gate 150, Chapter 10, Science/Kabbalah of the Animal Soul
The animal soul is understood from the classical medical and philosophical texts that were in use for thousands of years by the time Rabbi Hayim references them here. His usage of these texts and concepts shows us an integration and compliment between science and religion that is virtuous for us to copy today.
The animal soul is the moving soul, it moves by desires, not by external compulsion imposed by natural forces.
It is ruled by the physical senses and the powers of the mind, which include memory and imagination.
Once the physical senses experience anything, the mind records its as memory and it can them be ran through the imagination, and embellished, leading to all kinds of thoughts, be they of desire or simply abstract.
Nothing enters into the mind that does not first enter through the senses, examples of this are given.
Discussion also includes the arousal soul, and the nature of the good and evil inclinations and their relationship to the physical senses, and the mental faculties.