CHAPTER VI. 



CHOICE OF OBJECTIVES FOR REGULAR WORK. 



Practically, for the past four years, we have confined 

 ourselves to the use of four object-glasses, namely, an 

 inch or two-thirds inch of 45 or 50. A one-half inch 

 of 38. A one-sixth immersion, balsam angle ranging 

 from, say 87 to 95, according to the position of its- 

 collar, and a one-tenth immersion having a constant 

 angle of 100. Of the last two glasses, the one- sixth 

 has a working distance of one-fiftieth of an inch. The 

 one-tenth will work readily through covers one-one- 

 hundredth of an inch thick. 



The orthodox theory has been, and I suppose still is, 

 that each worker ought to select his stand, objectives, 

 accessories, etc., with special reference to the particular 

 line of investigations he may elect to pursue; and since, 

 as before intimated, there may be more or less force 

 attached to such a platform, I neither accept it nor reject 

 it; nor am I " on the fence," halting between two con- 

 flicting opinions. Without going into any special dis- 

 cussion of thdpros or cons, we will proceed to state the 

 character of the work in which we have been engaged, 

 accompanied with a recital of the special methods, etc., 

 employed. 



First, we use the microscope constantly from January 

 to December in examination of urinary deposits, and 

 for the study and detection of malignant growths. In 



