4 2 Modern Microscopy 



the leading manufacturers have vied with each other in 

 their attempts to provide inexpensive objectives that have 

 some of the most important qualities associated with 

 .apochromatism, particularly freedom from spherical aber- 

 ration; in so high a degree have they been successful 

 that the so-called students' series of objectives by many 

 makers, at what may be considered nominal prices, are in 

 many instances superior to the finest lenses of twenty 

 years ago. This improvement in the construction and 

 performance of the objective has brought in its train com- 

 plementary developments in the sub-stage condenser, and 

 necessarily increased accuracy and improved design in 

 the mechanical construction of the microscope- stand ; and 

 .any worker who is interested in the scientific and artistic 

 ;sides of microscopy can view with nothing but intense 

 satisfaction the distinctly progressive nature of everything 

 connected with the instrument itself and the absorbing 

 secrets it reveals. That this onward march will continue 

 is certain, for the issues which depend on the microscope 

 for their solution are ever increasing in number. The 

 demands that are made on it are more exacting and varied 

 than ever before, and there will always be forthcoming the 

 Avilling brain to devise facilities to meet them. 



The principal factors which have contributed to the 

 progress that has taken place in microscope construction, 

 optical and mechanical, are : Firstly, the unceasing criticism, 

 impartial examination, and, where merited, recommenda- 

 tion, together with the suggestion fraught of mature know- 

 ledge, skill, and thoughtful consideration on the part of 

 amateur microscopists, and especially a select number 

 whose names are familiar to every worker with the micro- 

 scope; secondly, to the exacting requirements of modern 

 bacteriological research, medical work generally, its adop- 

 tion in numerous branches of education, and in manu- 

 facturing industries of every description. 



Not many years ago a hospital rarely possessed more 

 .than one or two microscopes, and these were usually kept 



