1883. 83 Trafis. N. V. Ac. ScL 



the interpretation than on the supposed reticulum itself. In regard to 

 the first, i.e., seeing reticular structure, the verdict of independent mi- 

 croscopists has, in the majority of cases, been unfavorable. The best 

 authorities among those gentlemen have discussed and contested it. 

 That which is described by the founder of this doctrine, as threads 

 of a network, appears under the best objectives, well focussed, as a 

 mass of granules, irregularly heaped, more or less approaching each 

 other, and here and there leaving interstices ; but nothing is seen which 

 would mark a distinction between mere granules, distinctly attached 

 to each other, and a homogeneous line of thread. At tne locomotion of 

 an amoeba, the granules within flow along, more or less adherent to 

 each other, as globules of blood are seen to flow, attached to each 

 other, during circulation — nothing more. 



In regard to discrepancies in observation with the microscope, we 

 may be permittsd to refer here to the most remarkable discovery re- 

 cently made in optics by Prof. Abbe, which may throw light in the 

 future on many errors of observation with the microscope. Prof. Abbe 

 distinguishes two kinds of microscopic vision : one like the ordinary 

 vision, by rays directly from the object to the eye, which he calls 

 dioptric image: \.\\& o\\\&x,diffractive image, ^txo^nc&A by rays that 

 travel around the edge of a line or a minute object, so fine as to be but 

 a small multiple of a wave-length of light. These images are formed 

 by recomposition of the spectra, produced by these fine lines of objects. 

 They are less than 1-3000 of an inch. Since these granules are smaller, 

 the apparent blurred Hnes or threads are only diffractive images of gran- 

 ules. This would account for some objective errors. But are there not 

 also some subjective, personal errors, to be accounted for in microscopy, 

 as there exist in her sister science, telescopy — if astronomy may be 

 so termed, by analogy. We know astronomers have to allow for per- 

 sonal equation, errors owing to the difference in time between the im- 

 pression on the retina and the record by speaking or drawing, in dif- 

 ferent observers. May not microscopists be distinguished by individual 

 delicacies of vision ? Moreover there are other subjective errors, in- 

 dividual anomalies, to be accounted for. 



The fine pictures of Turner's, notwithstanding their beauty, have 

 encountered much severe criticism. In fact it has been ascertained 

 by Liebreich, who carefully examined Turner's gallery, that the painter 

 was affected by astigmatism, producing oddities in color and chiefly in 

 perspective, which formed the mcongruities in his art. So, too, the 

 great physicists of the future will doubtless determine the personal 

 errors of one nature or another, which have attended the labors of 

 former workers with the microscope. So much for the wondrous net- 

 work itself. 



