The physical Karma would be the act itself; the psychical Karma, the intention or the mental counterpart of the act; the spiritual Karma has relation to the harmony underlying all Nature. From the law of spiritual dynamics, elsewhere stated, it is clear that this classification is in the order of ascending power. The Karmic value of an act is the resultant of these three sets of forces. Suppose, for instance, that two persons do acts having the physical effect of producing blindness in the next incarnation, but with quite different effects on the two other planes. The result of the combination in one case will make blindness the curse of one's life, and in the other, produce some spiritual development which would otherwise never have taken place. So long as a man is alive, his consciousness is confined to the lowest plane - therefore, the effects of his Karma on the higher planes remain only as germs; but when, after death, his consciousness, overcoming the pressure of his earthward tendencies (represented by his passage through Kama Loka), ascends to the higher state of psychic and spiritual existence known as Devachan, the germs begin to unfold themselves, and keep the individual in that state until the unsatisfied physical Karma counterbalances the psychic and spiritual forces, and produces the next descent into objective life. The operation of this law is to be recognized within a limited sphere, in the production of what Darwin calls the differentiation of species. A change of environment leads to the elimination of useless organs and development of new ones, if the animal at all survives the change of conditions. Here we see how a strong desire to live under a given set of circumstances forces the body to mould itself accordingly. Similarly, the body which the ego acquires in its next incarnation is exactly suited to the unsatisfied physical cravings which the ego has brought forward from its previous incarnation. Acting under the impulse of these inclinations, the birth-seeking ego is attracted by the human couple, whose physical frames are capable of generating the required physical body. That portion of a man's Karma which acts through inherited tendencies is what is commonly called the law of heredity."
(Laura C. Holloway & Mohini Chatterji. Man: Fragments of Forgotten History. London: Reeves & Turner, 1885. pp. 124-26)