Body and Spirit
Lack of these particles results in a deficiency within the body. If they do not receive any of these particles at all, the result will be death. The compressed body formed of condensed particles, which is his corporeal while the revolution, action, and reaction of particles that always come and go, are the spirit. This notion is the terminology used since the old days.
However, the naming is not essential. What matters is that we can witness and are capable of comprehending. So, this distinction that people consider between body and spirit is insignificant; both originate from the same source and essence, and they are both of material. The one that is denser, we can see, and touch is called the physical body, and the other is the revolution and traffic of ethereal gases, which we cannot perceive (but cannot deny either) we call the spirit. Yes, this is the same force that theologians call the spirit. Nevertheless, the notion of spirit is nothing but a term.
It is that very actions and reactions in the body that no atheist individual can deny. It functions by breathing, entering the body by inhaling the particles in the air, and then releases them through exhalation, then by consuming foods and drinks, then discharging the waste from the body. The summation of these actions forms life.