272 T. F. SMITH ON TRUE VERSUS FALSE IMAGES IN MICROSCOPY. 



instance. You have here two membranes, in one of which is 

 imbedded longitudinal ribs connected with cross bars, from which 

 spring minute rod-like bodies to support and connect the other 

 membrane. Now, I cannot imagine a greater adaptability of means 

 to end, combining as it does the maximum of strength with the 

 minimum of weight, and is such a structure that any microscopist 

 who has worked it out and knows anything about construction 

 must feel to be absolutely truthful. The cross bars of some of the 

 scales of the Amathusia are not more than the 1 5 ^ 6 o of an inch 

 apart, and the rod-like bodies or " villi " are visibly projecting 

 from them. Between the coarseness of this scale and those of 

 Hipparclua Janira, the cross ribs of which are not less than 

 the loTro-oo" °f an ^ ncu a P ar ^» li es every gradation of fineness in 

 the scales of different species. I presume it is conceded that 

 cross bars the ^thro °f an mcn a P art is within the grasp of an oil- 

 immersion objective ; but will anyone tell me in cold blood that 

 when I see the same cross bars the ioo^jo'o °f an mcn a P al *t on a 

 scale presenting the same main features, that they do not exist? 



I have a very interesting specimen of a torn scale of the 

 Morpho Menelaus under a ^ in. oil-immersion. It is one of the 

 scales which reflects the intense blue light under a low power, and 

 which are, as a rule, all more or less damaged. This scale differs from 

 most in the fact that the longitudinal ribs are broad bands, and 

 the interspaces between them are very narrow, the reason being, I 

 presume, to present a large surface from which to reflect the 

 light. These bands are connected together with very slender 

 cross bars about the ^^q-^ of an inch apart. Now under the 

 pressure of mounting these bands get torn from each other and 

 twisted about in all directions, and from each edge projects the 

 ends of the torn strands. In the specimen under the microscope 

 part of the smooth membrane is torn away, and the bands under 

 are left projecting ; some still fastened together by the cross bars, 

 and some torn asunder, but showing the ragged edges where 

 torn. There can be no question here about the image being 

 truthful, unless we are prepared to part with our power of judging 

 cause and effect. In conclusion, given an object-glass capable of 

 showing a correct image of cross bars the ¥o J - - of an inch apart 

 on butterfly scales, what is to prevent it from showing discs in 

 voluntary muscle the -50000 °f an mcn a P arfc , Mr. Nelson's of the 

 n J 00 in., or any other structure with the same fineness of detail ? 



