karana sharira is a body or organism, which is capable of existing independently of the astral body. Its plane of existence is called sutratma, because, like so many beads strung on a thread, successive personalities are strung on this karana sharira, as the individual passes through incarnation after incarnation. By personality I mean that persistent idea of self, with its definite associations, so far as those associations appertain to the experiences of one earthly incarnation.
Of course all the associations or ideas of mental states which a human being may experience are not necessarily communicated to the astral man, much less to the karana sharira. Of all the experiences of the physical man, the astral man, or the karana sharira beyond it, can only assimilate those whose constitution and nature are similar to its own. It is, moreover, but consistent with justice that all our mental states should not be preserved; as most of them are concerned merely with the daily avocations, or even the physical wants of the human being, there is no object to be gained by their continued preservation. But all that goes deep into the intellectual nature of man, all the higher emotions of the human soul and the intellectual tastes generated in man with all his higher aspirations, do become impressed almost indelibly on the karana sharira. The astral body is simply the seat of the lower nature of man. His animal passions and emotions, and those ordinary thoughts which are generally connected with