Mental Bodies

[Plenum]

what are the mental bodies referred to in this quote?

In the realm of the mental bodies there are variations of mental energy transferred. This is, again, dependent upon the knowledge sought and the knowledge offered. The most common mental energy transfer is that of the teacher and the pupil. The amount of energy is dependent upon the quality of this offering upon the part of the teacher as regards the purity of the desire to serve and the quality of information offered and, upon the part of the student, the purity of the desire to learn and the quality of the mind vibratory complex which receives knowledge.