XXVIII, 4. Ott: A nevv Rotary Microtome. 451 



A new Rotaiy Microtome. 



The Problem of securing a satisfactory rotary microtome lias 

 been a serious oiie witli many laboratory workers , especially those 

 who are embedding in paraffin and working with serial sections. 

 The rapidity of cutting aud the ease with which the ribbon is formed 

 on a rotary microtome is a very desirable feature , but when one 

 must have sections oue after another of uniform thickness the 

 critical and painstaking man has often resorted to the laborious and 

 tedious method of cutting his series on a sliding microtome. 



To overcome the defects just mentioned the Spencer Lens Com- 

 pany went to work on the problem of producing a rotary microtome 

 which would add to the speed and convenience of tlj© ordinary 

 rotary microtome the accuracy and reliability of the Sloweä methods, 

 and at the same time to add other Very desirable features. 



Aside from a constructiou which in many instances has not 

 been sufticiently rigid the great source of error has heretofore been 

 the fact that the accuracy of the sectiou has depended on an ab- 

 solutely accurate fitting of the block which carries the specimen to 

 the Support on which it moves up and down. From a raechanical 

 Standpoint it is impossible to fit this block to the upright support 

 so that there is absolutely no side movement and at the same time 

 permitting a free up and down excursion. 



This contiugency has been met in the Spencer microtome by 

 making the part which holds the object clamp (SP^ fig. 2) slide 

 freely backward and forward on the block [B) whicli moves up and 

 down on the support {S). One end of this part {SP) is a polished 

 inclined plane surface which is held by a spring against the point {P) 

 projecting from the block {FB) which moves from side to side on a 



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