IV 



PREFACE 



the retinal image, whether it is made with or without the aid of a microscope, 

 must always depend upon the character and training of the seeing and appreciat- 

 ing brain behind the eye. The microscope simply aids the eye in furnishing raw 

 material, so to speak, for the brain to work upon. (From 3d ed.) 



Grateful acknowledgment is made to the opticians and instrument makers 

 for the loan of cuts and for courteous and complete answers to numerous questions ; 

 to the directors of laboratories in different parts of the country, to his colleagues 

 in the departments of Physics, Chemistry and Electrical Engineering in Cornell 

 University ; and finally to his pupils past and present who have given their support 

 and encouragement. 



Inclosing I would like to urge those who are interested in Microscopy to take 

 some microscopical journal, and if possible to become a member of some micro- 

 scopical club or society. One can do very little alone, but by helping others 

 and being helped in return, the workers in any field of human endeavor can 

 accomplish great things. 



SIMON HENRY GAGE, 

 CORNEI,!, UNIVERSITY, 



October /, 1901. ITHACA, N. Y. , U. S. A. 



PREFACE TO THE NINTH EDITION 



In this edition important changes have been made on pp. 7-8, to the parts 

 relating to serial sections and to micro-chemistry. 



The chapter on the projection microscope has been entirely rewritten and 

 much more fully illustrated. With the good apparatus now available it is hoped 

 that teachers will make more use of this excellent method of demonstration. 



Due to the courtesy of the manufacturers excellent pictures of the latest 

 microscopes and apparatus are presented in this edition. It can but be a cause for 

 rejoicing to the multitudes who now use the microscope to see the beauty of form 

 which it has attained. 



February /, 



