ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



399 



Fig. 65. 



Wasserlein's Saccharometer Microscope.* — This instrument is 

 shown in Fig. 65, and its special feature (though one of very doubt- 

 ful advantage) is that it enables one and the same instrument to be 

 used as an ordinary Microscope and as a saccharometer. 



The following is the method of using it : — The diaphragm having 

 been removed from the stage t, and the polarizer p substituted, the 

 body-tube (with eye-piece and objective) is taken out of the tube r, 

 and the saccharometer- tube sr in- 

 serted so that its lower end is close 

 over the polarizer. The latter tube 

 has at its upper end, and on one 

 side, a semicircle sk fixed at right 

 angles, on which is a scale gradu- 

 ated up to 25° from the centre on 

 either side. The analyzer aa is 

 inserted, and the mirror s arranged 

 in the usual way for microscopical 

 observation. The nonius n, at- 

 tached to the analyzer, is then 

 adjusted by turning the latter so 

 that the centre division of the 

 nonius exactly agrees with the 0° 

 of the scale, and the polarizer is 

 revolved on its axis to the right 

 or left until the so-called neutral 

 point is reached, at which both 

 halves of the field of view appear 

 of equal intensity and colour. Ee- 

 moviug the analyzer, the glass 

 cylinder ^ (20 cm. long) is inserted 

 into the saccharometer-tube (being 

 first completely filled with clear 

 solution of sugar or urine), and the 

 analyzer replaced in its original 

 position. On revolving it to the 

 right or left until the neutral point 

 is again reached, the nonius will 

 now have another position on the 

 scale, and its central division marks 

 the degree, from which the per- 

 centage of sugar in the solution can 

 be determined. A petroleum lamp 

 is the best for the observation. 



The glass cylinder g must be completely filled, so that after being 

 closed by the cap h there are no air-bubbles. 



The scale (not divided into 360^ but into 180^) shows the quantity 

 of glucose or grape-sugar direct. 



Cf. Hager, H., ' Das Mikroskop ' (8vo, Berlin, 1879), pp. 45-7, 1 fi^ 



