PREFACE.

more strange, in a pretended age of reason and of scientific progress, than to find a discovery so simple, yet so prolific in its consequences—a discovery which was intended to throw so much new light on our knowledge of human nature and the flexibility of the animal organism in general, and to increase our therapeutic powers—to see such a discovery confined within the narrow circle of a small number of inquisitive individuals, who made no mystery of the knowledge they had acquired, yet who dared not speak of the truths they had discovered and embraced without exposing themselves to the scorn or ridicule of powerful and influential antagonists, even among those who were otherwise learned and talented?

Had the question related merely to certain uncertain theoretical notions, or to the adoption of some novel system of abstract truths, we might easily conceive that there might have been ample materials for controversial discussion; but here the subject in dispute was merely a matter of fact, which was capable of being almost immediately verified or disproved by a direct appeal to experiment and observation; and, moreover, the related investigation was exceedingly simple and, besides, open and accessible to all the world.

But it would appear that a large majority of the learned men of the age were, for one reason or