vi INTRODUCTION. 
affairs. No such elementary but comprehensive work | 
. exists in English among the numerous able treatises upon 
special branches of the subject. The present volume is | 
therefore the outgrowth of a pedagogic need. The book 
is necessarily incomplete from the standpoint of the 
expert in any of the branches which it treats, but if it 
conveys to the student’s mind such an idea of the possible 
applications of the microscope in varied fields as shall 
stimulate him eventually to the further exploration of 
some one of them, it will have served its purpose. 
In the preparation of this volume, the authorities 
quoted in connection with the various chapters have been 
freely drawn upon. The author further desires to ex- 
press his grateful obligation, to Dr. P. G. Stiles for the 
preparation of original drawings; and for advice and 
assistance in regard to various portions of the manuscript 
to Professor W. T. Sedgwick, Professor Mary A. Willcox, 
Professor H. M. Goodwin, Professor F. J. Moore, Pro- 
fessor C. H. Warren, Dr. C. C. Simmons, Mr. A. E. 
Leach, Mr. A. G. Woodman, Dr. E. L. Walker, and 
Miss A. F. Rogers. 
Acknowledgments are due to the authors and pub- 
lishers of the following books for figures which have 
either been copied directly or redrawn: 
DESCHANEL, A. P., and EVERETT, J. D. Elementary Treatise 
on Natural Philosophy. New York, Appleton & Co., 1894. 
HaGER, H., and MEz,C. Das Mikroskop und seine Anwendung. 
Berlin, J. Springer, 1899. 
CARPENTER, W. B., and DALLINGER, W. H. The Microscope 
and its Revelations. London, J. & A. Churchill, 1891. 
GaGE, S. H. The Microscope. Ithaca, Comstock Publishing 
Co., 1904. 
