250 Transactions of the 



III. — Structure of Battledore Scales. 



By J. Anthony, M.D., F.R.M.S. 



(Bead before the Royal Microscopical Society, May 1, 1872.) 



I VENTURE to make some further observations on the structure of 

 Battledore scales, inasmuch as, through the kindness of Mr. Mclntire 

 and Mr. Wonfor, I have been enabled to examine carefully a number 

 of species of the Lycsenidae, to which these scales are peculiar ; and 

 more particularly do I bring this matter forward, because in making 

 such examination I employed a mode of illumination which I found 

 so very useful, that I would call the attention of the Society to it, 

 as a valuable addition to our present means, for the investigation of 

 structm-e under the microscope. 



I will take this illumination first, as on it mil partly hinge the 

 correctness of what I have to describe with respect to the scales. In 

 looking then at the various forms of these Battledore scales, it of 

 course was desirable to make out clearly the structure on the sur- 

 face by " reflected " light, in order to check the suspected fallacious 

 appearances given under " transmitted " hght. Now a ^th objective 

 entailed such an amount of obhquity of light with respect to the 

 plane of the object, that shadows, quasi rugosities, and possible ex- 

 traneous matter on the surface of the scale became unduly prominent, 

 60 that very small bodies, such as the tubercular elevations I was 

 seeking, were lost in all these exaggerations of light and shadow. 

 Under these circumstances I bethought me of applying a device, 

 often resorted to in practical astronomy, in the examination of close 

 doubled stars, where the extreme contrast of brilhant hght against 

 a dark ground produces much confusion of vision, the said device 

 for getting rid of this consisting in illuminating the field of the 

 telescope artificially just to such an extent as to reduce the violent 

 contrast, without impairing the hrightness of the image. My 

 adaptation of this principle to the microscope was accomplished in 

 the following way : I illuminated the surface of the scale vividly 

 from the side, by means of the usual plano-convex lens, and then, 

 reflecting some light (by my mirror below the stage) through the 

 condenser, I gradually brought that condensed light up to just so 

 much brightness, as to very faintly illuminate the field and the 

 object. The effect was all I could desire ; the exaggerated shadows 

 were done away with, the dominant illumination was still reflected 

 from the object, and a careful balancing of these lights gave me the 

 Battledore scales with a beauty, and the markings on their surfaces 

 with a reality, which I had hardly ventured to expect. I suppose 

 I may call this device " double illumination," and I take the em- 

 ployment of it for the microscope to be a novelty, as I have never 

 heard of, or read of, its being so employed ; however, remembermg 

 the Solomonian proverb that " There is nothing new under the sun," 

 I dare say somebody will start up and say he has used this mode of 



