MICROSCOPICAL DIAGNOSIS. II 



decreases, as the square of the angular aperture increases. This 

 quality of an objective is exceedingly desirable, even essential for 

 some kinds of work; hence different observers over or under-value 

 it according to the nature of their work. 



The "field" includes all the circle of light presented to the eye 

 through the microscope. It is said to be flat when the object shows 

 equally well over every part of the field, without changing the 

 adjustment. If the field be perfectly flat, then the lines of a stage 

 micrometer should be equally as sharp and distinct at the periphery 

 as at the centre. 



Having reviewed, briefly, the stand, the eye-piece and the 

 objective, we are now prepared to answer the question what 

 microscope is best adapted to the needs of the busy practitioner 

 and the no less active pharmacist? 



The expert is able to choose for himself; we only venture 

 advice to the inexperienced. In the first place, the stand should 

 have a good, smooth, coarse adjustment, with as perfect a fine 

 adjustment as it is possible to obtain. An object-carrier or movable 

 stage is very desirable. Two eye-pieces should accompany the 

 stand, and an "A" and "C" cr Nos. i and 3 will meet the demands. 



Two objectives will answer all purposes for a long time. Our 

 experience would say: Purchase an one-inch objective of about 25 

 angular aperture, and an one-fourth inch of about 100 angular 

 aperture; or a three-fourths inch of about 35 and an one-fifth of 

 about 100. These are not expensive glasses, and yet they will do 

 fine enough work of the kind for which they are recommended. 

 We have seen good glasses of still lower angles. Having taught 

 over four hundred students a year, for a number of years, practical 

 laboratory work, and having purchased for them a very large num- 

 ber of microscopes, we are prepared to believe that an instrument 

 as described above, is one of the best outfits of the kind a physician 

 or pharmacist can purchase. 



Such an instrument, with a few accessories, as a condenser, for- 

 ceps, slides and covers, can be purchased for a sum ranging between 

 $50 and $75. Thus the old excuse that "too great an outlay is 

 needed at the start," will no longer remain valid; and with such a 

 number of hand-books in the market the beginner need not suffer 

 for helps. 



From the great list of accessories a few only must receive 



