Intro.] 



INTRODUCTION 



Cornea 



Lena 



ber of original workers emanating from our schools will vary as prac- 

 tical work is favored or discouraged. It is certain that they who are 

 most fully conversant with elementary details, 

 and most clever at demonstration, will be most 

 successful in the consideration of the higher and 

 more abstruse problems, and will feel a real love 

 for their work which no mere superficial inquirer 

 will experience. It is only by being thoroughly 

 grounded in first principles, and well practised 

 in mechanical operations, that any one can hope 

 to achieve real success in the higher branches of 

 scientific inquiry, or to detect the fallacy of 

 certain so-called experiments." 



And Hon. J. D. Cox, skilled alike in the arts of 

 war, statesmanship, and science, in his notable 

 address upon Systematic Instruction in the Micro- 

 scope at the University, before the American 

 Microscopical Society, in 1893, says: "I wish to 

 urge the desirability of a somewhat extensive 

 course of technical training in regard to the micro- 

 scope. . . . Any one who desires to devote him- 

 self seriously to investigation with the microscope 

 will find great advantage, as it seems to me, in de- 

 voting some time to the study of the instrument 

 itself in all its parts, and the history of their de- 

 velopment." The study of this whole address is 

 urged upon the person interested in the just ap- 

 preciation of the different parts of the microscope 

 and their successful employment or improvement. 



Sir A. E. Wright, in his book "Principles of 

 Microscopy," says this: "Every one who has to 

 use the microscope must decide for himself the 

 question as to whether he will do so in accordance 

 with a system of rule of thumb, or whether he 

 will seek to supersede this by a system of reasoned action based upon 

 a study of his instrument and a consideration of the scientific prin- 



Object 



Fig. 2. A Simple 

 Microscope Help- 

 ing the Eye to 

 Form a Retinal 

 Image of a Near 

 Object. 



Object The object 

 to be seen by the 

 eye. 



Lens The double 

 convex lens acting 

 as a magnifier or 

 simple microscope 

 to aid the eye in see- 

 ing a near object. 



Cornea The cor- 

 nea of the eye. 



r The single re- 

 fracting surface in 

 the schematic eve. 



cl The crystalline 

 lens of the eye, also 

 the center of the re- 

 fracting surfaces or 

 the nodal point of 

 the eye where the 

 se< ondary axial rays 



cross. 



ri Retinal image; 

 it is inverted. 



