when such a rapid accumulation of facts is taking place, as there is in ours, we are doubly bound to render our knowledge accessible to the whole body of our professional brethren. We would have reform, and not revolution : we would preserve the old, and add the new. But our contemporaries have a confused idea of the results of our activity. For only too much it is apt to appear as though nought but a confused and motley mass of old and new would thereby be obtained ; and the necessity of combatting rather the false or exclusive doctrines of the more modern, than those of the older writers, produces the impression that our endeavours savour more of revolution than reformation. It is, no doubt, much more agreeable to confine oneself to the investigation and simple publication of what one discovers, and to leave to others to "take it to market" (verwerthen—exploiter), but experience teaches us that this is extremely dangerous, and in the end only turns out to the advantage of those who have the least tenderness of conscience. Let us undertake, therefore, every one of us to fulfil the duties both of an observer and of an instructor.
The lectures, which I here publish with the view of accomplishing this double purpose, have found such very patient auditors, that they may perhaps venture to hope for indulgent readers likewise. How greatly they stand in need of indulgence, I myself feel very strongly. Every kind of lecture can only satisfy the actual hearers; and especially when it is chiefly intended to serve as an explanation of drawings on a board, and microscopical preparations, it must necessarily appear heterogeneous and defective to the reader. When the intention is to give a concise view of a comprehensive subject, it necessarily becomes impossible to bring forward all the arguments that could be advanced, and to support them by the requisite quotations. In lectures such as these too the personal views of the lecturer may seem to be brought forward with undue exclusiveness, but as it is his business to give a clear exposition of the actual state of the science of which he treats, he is obliged to define with precision the principles, the correctness of which he has proved by his own experience.
I trust therefore that what I offer may not be taken for more than it is intended to be. Those, who have found leisure enough to keep
