Voronoff is very candid in admitting that his interest and enthusiasm may cause him unconsciously to overestimate the rejuvenating effects of his grafts, and he also admits that he does not yet know how long the beneficial effects will last. That they have done so for two or even three years is beyond question. He is conscious of the incredulity of biological experts but reminds them that a society of physicists, when first shown the phonograph, insisted that it was ventriloquism. He calls attention to the great difficulties in his field, due not only to prejudice but to laws that forbid the taking of organs of healthy men killed by accident. He does not expect surgery will ever remove glands or even portions of them from the living young to revitalize the old, in human subjects, although he thinks that perhaps “the restoration of the vital energy and the productive power of Pasteur may well be worth the slight pain inflicted on the robust porter.” Most men, however, would prefer to lose an eye rather than one of these glands, as the price proposed by a few who offered themselves for this purpose shows. Voronoff sees a great future possible for glandular transplantation and grafting between men and animals but shows that this can never be very effective for man save with apes, to whom he is so much more closely related, even in the makeup and properties of his blood, than to any other species. Thus the organ of an ape transplanted to man will find there nutritive and other conditions very like those it was used to. Surgery has done much and wonderful grafting in the war, even of bones, and now man, “the talented ape,” as Huxley called him, is recognizing his simian ancestry in a new way. A fibula congenitally missing in a child was successfully transplanted from an ape, and the radiogram showed complete intussusception, no absorption, and it functioned well. Voronoff transplanted the thyroid gland of an ape into the neck of a boy of fourteen, who was lapsing to cretinism, with remarkable results which he describes in detail and with photographs, although the ape from which the thyroid was taken died. The transplanted gland was not merely tolerated and then expelled as a foreign body or resorbed but the graft seemed to really take and its effects to be permanent and not temporary, like those due to the ingestion of thyroid tablets. The boy changed in his habits, his school work improved remarkably, and the last heard from him was that he was a soldier at the front. Here the beneficial effects were marked and traced for six years and seemed to promise permanence. Other grafts from apes for cretinism have been made, but because chimpanzees, which are best for this purpose, are very hard to procure in sufficient numbers, this process must always be limited. Voronoff has, however, made no grafts, even of thyroids, from parent to child save in one case; and here, although the young imbecile was nearly twenty when the operation was performed, marked