346 



SUMMARY OF CUKEENT KESEARCHES RELATING TO 



Nelson's article iucidentallj includes personal and other references 

 to many important steps in Microscope evolution during the last forty 

 years. Among them may be mentioned : — Swift's three-pin facility 

 nosepiece (figs. 56 and 57) ; rack-work draw-tube for objective adjust- 

 ment ; Michael Foster's report on " Modern Microscopes, with a special 

 view to the requirements of Medical Students and Practitioners," with 

 criticisms of the chief types of his day ; the Zentmayer fine-adjustment 

 and its application to various Microscopes ; the swinging substage as 

 designed for the so-called resolution of diatoms by oblique light ; Abbe's 

 opposition to full-cone illumination ; springing in Microscope con- 

 struction. 



Reichert's riuorescence-Microscope.* — A fluorescence-Microscope 

 gives a new means for the examination of bodies in a condition of self- 

 luminosity. The light-source is obtained as the result of passing a 



Fig. 60. 



strong beam from an arc-lamp through a Wood's filter, as improved by 

 Lehmaun, which cuts out all visible light, and only transmits ultra- 

 violet rays up to 350 ynyn. The parts of the apparatus are set up in the 

 following order : — Light-source (as above), quartz-illuminating lens, 

 filter, Microscope with quartz-condenser and dark-ground illumination. 

 The arrangements will be understood from fig. 60. For the observation 

 of the fluorescence-image ordinary objectives and oculars are employed. 

 The light issuing from the source, freed by means of the filter from the 

 visible rays, and concentrated by means of the quartz-illuminating 

 apparatus on the preparation, brings the object into a condition approxi- 

 mating to self-luminosity. If the dark-ground apparatus were not 

 introduced, the image would appear as if viewed through a blue veil. 

 A quartz mirror condenser is found, however, to be unsatisfactory, as 

 the silver layer has but small reflective power for ultra-violet. A new 

 condenser of magnalium, designed by von Weimarns, has been tried^ 



* Zeitschr. f. wiss. Mikrosk., sxviii. (1911) pp. 330-7 (1 fig.); Physikalisch. 

 Zeitschr., xii. (1911) pp. 1010-11. 



