XIV INTRODUCTION. 



long acknowledged the microscope as one of its most efficient as~ 

 sistants, and in the practice of the best physicians it is regarded as 

 an indispensable means of diagnosis in ome diseases. 



4. As an assistant in the arts. Its importance in this department 

 is but just beginning to be recognized, and in a former paragraph 

 we have endeavored to point out a few of the subjects to which it 

 may be applied with good hopes of success. 



These important and obvious advantages are not difficult to secure, 

 provided we avoid two mistakes which are very commonly made by 

 beginners. One of these consists in supposing that it is only by 

 means of very expensive and complicated instruments that anything 

 of value can be accomplished in microscopy. Now while it is cer- 

 tain that, in some departments of study, none but the very best 

 microscopes are of any value at all, it is equally certain that a very 

 wide range of study and of practical work can be thoroughly culti- 

 vated by means of apparatus of very moderate cost, and of great 

 simplicity of construction. The great discoveries of Ehrenberg, 

 which opened up entire new fields of research and of thought, were 

 made with a microscope which at the present day would not com- 

 mand $25. Indeed some of the French instruments that are sold 

 for $15 will show a very large proportion of the objects that are 

 figured in his earlier works. Most of the great anatomical ar;d 

 botanical discoveries were made with simple microscopes of no great 

 power, and it is not many years since one of the most successful 

 workers in the field of botany gave it as his opinion fiat a power of 

 300 diameters is capable of showing everything that is of impor- 

 tance in this science. 



The other error is of precisely the opposite kind. It is not at all 

 unusual to meet persons who seem to think that all that is necessary 

 in order to become a microscopist is to buy a microscope and place 

 objects under it! Such people always entertain an exaggerated idea 

 of the power of the microscope as an instrument of research. For 

 example, they think that in order to detect adulteration all that is 

 jpecessary is to place a sample under the microscope, when all im- 

 purities will at once stand out conspicuously! To their imagination 

 every blood corpuscle is clearly marked with the name of the animal 

 from which it was obtained! * 



Truth lies between these extreme's. No progress can be made 

 without steady application and persistent labor, but any person of 

 fair average ability and a moderate degree of perseverance can soon 

 learn to follow the beaten track at least, if not to branch out into 

 original research. 



