200 METHODS OP MICROSCOPICAL RESEARCH. 



Distance 22-J- inches. Miall's plate. 1 min. Pyro. 

 Over-exposed. 



Human Kidney injected carmine. Transverse 

 Section in Balsam. Object yellowish. 1 inch objec- 

 tive by Stanley. Distance 36 inches. " German ' 

 plate 1^ min. Oxalate. Correct exposure. 



" Tongue " of Blowfly. Balsam. J inch objective 

 and achr. condenser. Distance 40 inches. Lancaster's 

 plate. 1^ min. Oxalate. Correct exposure. 



Spicules of Synapta. Dark ground illumination 

 by spot lens. 1 inch objective by Stanley. Dis- 

 tance 41 inches. " German " plate. 2 min. Oxalate. 

 Correct exposure. 



Salicine. Polarized light. Crossed nicols. With- 

 out selenite. 1 inch objective. Distance 20 inches. 

 Home made plate. 2^ inin. Oxalate. Correct 

 exposure. 



Ctenoid scales. Skin of sole. Dry, as opaque 

 object. White, but under cover-glass, and therefore 

 loss of light by reflection. Light condensed as 

 usual, but incident at about 10. 3 inch objective of 

 12 by Browning. Distance 28 inches. Miall's plate. 

 5 min. Pyro. Correct exposure. 



These examples have been selected as illustrative 

 of very various objects, magnifying powers and 

 modes of illumination. Opaque objects are the 

 most difficult, on account of the trouble of focussing 

 by the small amount of light they reflect. 



Although any object glass may be used for this 

 work, some possess qualities which specially fit 

 them for it, and there are others in the same degree 

 unsuitable. The most important properties of an 

 objective for photographic work good definition 

 being, of course, pre- supposed as essential for all 



