REVIEW. 



The Microscope and Microscopical Technology. By Dr. 



H. Frey, translated by G. R. Cutter, M. D., from the 



fourth German Edition. New York, 1872. London, 

 Sampson Low and Co. 



The admirable text-book of Professor Frey is too well 

 known to require any lengthened eulogium at our hands. It 

 has long been familiar to all histologists acquainted with the 

 German language, and we must now congratulate English 

 readers on having it presented in a form accessible to them. 



Dr. Frey follows the practice of other writers on the micro- 

 scope in prefixing a general account of the instrument itself, 

 and the methods of observing with it. This appears to us to 

 be the least satisfactory portion of the manual. The optical 

 part is, perhaps, sufficient, but barely so ; that relating to 

 the use and manipulation of the microscope is in several 

 respects defective. For instance^ in the case of " correction" 

 for thickness of cover-glass some description is given of the 

 apparatus, but it is hardly explained, and no practical direc- 

 tions for using it, so that a student relying on Professor 

 Frey's instructions would find himself much at a loss, or 

 obliged to use his ^' correction^^ by mere guesswork. The 

 subject of illumination is also treated in a very cursory 

 manner, some of the English condensers being figured, but 

 not explained ; and though this, of course, is a less important 

 matter in Germany, where artificial light is more rarely used 

 than with us, still some of these contrivances are practically 

 indispensable for displaying the minutiae of high-power defini- 

 tion, which Professor Frey afterwards shows that he does not 

 despise. 



It was, of course, natural that English microscopes should 

 receive little notice, since the work was originally intended 

 for German observers and students. The translator has 

 hardly supplied this deficiency, even for American readers, 

 by his lengthy account of the history of microscope- making 

 in the United States. 



There is a tolerably full account of test objects, and their 

 influence in the improvement of the microscope. The author 



