OF ELEMENTARY PRACTICAL PHYSIOLOGY, BY M. FOSTER, M.D., F.R.S., PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OF CAMBRIDGE. AND J. N. LANGLEY, M.A., F.R.S., FELLOW OF TRINITY COLLEGE, CAMBRIDGE. FIFTH EDITION. London MACMILLAN AND CO. [All Rights reserved.] PREFACE TO FIFTH EDITION. THE present Edition does not differ materially from the preceding ones, though its bulk has been somewhat increased by the introduction of new matter. The opinion of past years has strengthened our opinion that it is above all things undesirable to attempt to teach all the members of even an Elementary Class in exactly the same way; in some cases it is necessary to confine the instruction to a certain beaten track and to make the teaching a formal drill; in other cases considerable latitude may profitably be allowed, and the student encouraged to diverge from the more common path. By the additions which we have made, we hope to have rendered the volume useful to both these classes. we have not attempted to indicate in any way what parts are to be considered as fundamental and necessary, and what as supplementary and optional. We have given various methods in fuller detail than formerly ; but we must leave to the teacher, who is led to use the book, to decide whether this or that operation shall be carried out by him or entrusted to the student himself. But |