impossible to imagine that the gland secretions of the two different glands, which bring about the full development of secondary sexual characters which are obviously present from the first, should remain only on one side of the body. They must, in fact, be carried by the blood to all the cells of the body. Nevertheless, the secretions of the male gland pass only to those cells which have "male" properties, and vice versa, the secretions of the ovary affect only the cells of the "female" half of the body.
Strong support for this view of a specific cell structure is supplied by the numerous experiments on transplantation. The surgeon nowadays tries, as much as possible, to retain the full strength of the functions of every organ, and, if some of the tissues are missing, he seeks aid in substitutes. It is found that only those tissues graft which are taken from the same species, while still better results are obtained by the use of parts of the same individual. Heteroplasty, i.e., the attempt to graft foreign tissues, has never succeeded. A body requires cells in harmony with itself. If they are in close relation, as is the case in tissues of the same species—even the individual has its own type—then it is very probable that with time the newly grafted tissue will, by means of reconstruction, assimilate itself with the other cells of the same organ, and so eventually with the entire organism.
