He then passes to scientific demonstration. Is there, he asks, a material bond, a bodily, living, and enduring tie, between human beings of all lands and all ages?[63] He finds a proof that there is such a bond in the researches of Weismann and in that writer's theory of the germ plasm, which has now become classic.[64] In each individual, the cells of the germ plasm continue the life of the parents, of which, in the fullest sense of the word, they are living portions. They are undying. They pass, changeless, to our children and to our children's children. Thus there really persists throughout the whole genealogical tree a part of the same living substance. A portion of this organic unity lives in each individual and thereby we are physically connected with the universal community. Nicolai points out, in passing, the remarkable relationships between these scientific hypotheses of the last thirty years and certain mystical intuitions of the Greeks and the early Christians--"the spirit (pneuma) that quickeneth" (Saint John, vi, 63), the generative spirit, which is not only distinguished from the flesh, as Saint John declares, but is likewise distinguished from the soul, as appears from a passage in Saint Paul's first epistle to the Corinthians (xv, 44), where the "spiritual body" (soma pneumatikon) is contrasted with the "natural body" (soma psuchikon). The spiritual body is declared to be more essential than the natural body (the psychical or intellectual body); and the former really and materially penetrates the bodies of all men.