2fi8 T. F. SMITH ON TRUE VERSUS FALSE IMAGES IN MICROSCOPY. 



possesses two or three sets of stria? ; whether striation exists at 

 all ; whether the visible delineation is caused by isolated pro- 

 minences or depressions, &c, no microscope, however perfect, no 

 amplification, however magnified, can inform us." Then further 

 on he states : " That the same state of things obtains in numerous 

 instances of organic forms, the study of which belongs to the pro- 

 vince of histology, we may learn from the instance of striated 

 muscular fibre. The manifold changes in the character of the 

 images which present themselves, account, to a certain extent, for 

 the notorious discordance between the different observers, and 

 prove also the impossibility of acquiring any definite knowledge of 

 their actual physical structure." 



I think you will admit that this is not a mere sprinkling, but a 

 regular deluge of doubt with whieh to quench the ardour of the 

 investigator intent on forcing Nature to give up her secrets, and 

 even Dr. Abbe seems to be frightened at the logical outcome of 

 his own theory, for further on he says : " It is obvious that a 

 perfect fusion, in every case of the several diffraction images, and 

 then an exact superposition of the resultant diffraction image upon 

 the absorption image, is only possible when the objective is uni- 

 formly free from aberration over the whole area of its aperture." 

 This clearly means that given perfect correction of the objective 

 there is perfect definition of the object, which to me seems to con- 

 tradict the former part of the paper. I trace in all Dr. Abbe's 

 subsequent papers the influence of two moods, and that at times he 

 could not resist the evidence, as the aperture of the objectives 

 became larger, that the image given by them was a truthful one. 

 As formulated by him in his paper on the " Estimation of Aperture 

 of the Microscope," the Diffraction Theory stands thus : " Perfect 

 similarity between the microscopical image and the object, or the 

 enlarged projection of the object by the microscope, always depends 

 on the admission to, and utilization by the objective, of the whole 

 of the diffracted rays which the structure is competent to emit. 

 When a portion only of the total diffraction fan appertaining to a 

 given structure is lost, the image is more or less incomplete or 

 dissimilar. When a portion only of the whole diffracted light 

 from a structure is utilized, the image is a true enlarged projec- 

 tion of a different structure * namely, one of the whole of whose 

 diffracted beams would, if it physically existed, be represented by 



* These italics are mine. — T. F. S. 



