ADJUSTABLE OBJECTIVES. 151 



(and such are described in this little book). Now, as 

 to objectives. You can do all the work named with a 

 one-inch of tolerably low angle, costing you, say, some 

 $7.00; and a real good three-tenths of 70 aperture, 

 which will cost you, say, $11.00. The chances are, 

 however, that as you become familiar with the use of 

 the instrument, thereby learning its value to you in 

 your daily professional practice, you will feel an inclin- 

 ation to dip somewhat deeper into the problems which 

 will most assuredly surround you. In your examina- 

 tions of urines, you will get glimpses of bacteria ; you 

 may meet with structures which you are almost assured 

 are " pale hyaline " tube casts ; and you naturally desire 

 a little more amplification and definition thereon to 

 enable you to pronounce with certainty. In fact, you 

 now want such a glass as a dry one-fourth of 110 or 

 120, and adjustable. Now, to use this glass to advan- 

 tage, you have first to become familiar with its manipu- 

 lations. It will be requisite that you arrive at some 

 knowledge of this before such an objective can be of 

 much avail to you. Now, if you purchase the one- 

 fourth recommended, you will still have room for the 

 employment of the three-tenths, but you will have to 

 study the use of the one-fourth just the same as if you 

 had never seen an object-glass. Hence, I had rather 

 recommend that you purchase the one-fourth at the 

 start, and thus get early accustomed to the use of ad- 

 justable glasses ; and in this latter case it will almost 

 assuredly occur that you will eventually desire to 

 employ glasses of the widest apertures, and the expe- 



