Journal of 



Applied Microscopy 



and 



Laboratory Methods. 



VOLUME IV. 



JUNE, 1901. NUMBER 6 



Improved Automatic Microtomes. 



The two microtomes, to which I wish to call attention, are modifications of 

 the two forms of automatic microtomes described by me in 1897.^ In neither 

 instrument have the essential features of the construction been changed, but the 

 alterations made were introduced partly to increase the accuracy of the cutting, 

 partly to facilitate the manipulation of the apparatus. Messrs. Bausch & Lomb 

 undertook the series of improvements at my request, and I am indebted espec- 

 ially to Mr. Edward Bausch for the time and thought he has given both to plan- 

 ning and executing the work involved. Every detail has been the subject of 

 extended consultation, but I wish the pleasure of acknowledging that several 

 valuable innovations were first suggested by Mr. Bausch. The new feed for the 

 precision microtome was devised and worked out by Messrs. Bausch & Lomb. 



I. THE AUTOMATIC WHEEL-MICROTOME. 

 Perhaps the most important improvement in this instrument is its increased 

 accuracy, which has been secured by the use of the finest machine tools for 

 planing the sliding surfaces, cutting the micrometer screw and cutting the 

 teeth of the feed wheel. The accuracy is now so great that one can cut easily a un- 

 iform series of sections of two microns in thickness, and presumably of one micron, 

 but the one micron sections I have not sufficiently tested. In the former instru- 

 ments, both American and German, the sections would skip occasionally, and 

 then the following section would be of nearly double thickness and the uniform- 

 ity of a series ruined. With the present instruments, three of which I have 

 tested, this vexatious irregularity does not occur, at least with ordinary objects. 

 I have not yet tried the microtome with objects specially difficult to cut. 



Other improvements have rendered the microtome more convenient to use. 

 The following five changes are most important : First— i:h& toothed wheel 

 which supplies the automatic feed has been enlarged and cut to have five- 

 hundred teeth, so that, as the micrometer screw has a half-millimeter pitch, each 

 tooth equals a feed of one micron. 6'^^^//^/— The automatic feed has been so con- 

 trived that it will give any desired thickness, from one to twenty-five microns, 

 and can be changed in a moment. This is accomplished by having the pawl- 



1 Science, Vol. V, No. 127, pages 857-866, June 4, 1897. 



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