known and unknown laws of sexual affinity, and which also varies with the degree of specific, racial and family relationship, and with the health and absence of deformity in the two individuals, and which, finally, will become smaller as the actual spacial distance between the two is greater, and which can be determined in any individual case.
When in this formula A must be infinity; this is the extreme case; it is sexual attraction as an elemental force, as it has been described with a weird mastercraft by Lynkeus in the novel "Im Postwangen." Such sexual attraction is as much a natural law as the downward growth of a rootlet towards the earth, or the migration of bacteria to the oxygen at the edge of a microscopic cover-glass. But it takes some time to grow accustomed to such a view. I shall refer to this point again.
If has its maximum value, which is when it equals unity, then .
This would be the extreme case of the action of all the sympathetic and antipathetic relations between human beings (leaving out of account social relations in their narrowest sense, which are merely the safeguards of communities) which are not included in the law of sexual affinity. As K generally increases with the strength of congenital relationship, A has a greater value when the individuals are of the same nationality than when they belong to different nationalities. The value of f' is great in this case, and one can investigate its fluctuations, as, for instance, when two domestic animals of different species are in association; at first it usually stands for violent enmity, or fear of each other (and A has a negative value), whilst later on a friendship may come about.
When K = o in the formula
then A = o, which means that between two living beings of origin too remote there may be no trace of sexual attraction.
