Microtomes : their Choice and Use 231 



tomes of home manufacture, and the choice is lamentably 

 limited. 



British Microtomes. — With the exception of a few instru- 

 ments adapted for special work, there is nothing of- British 

 manufacture to command attention. This lack is greatly 

 to be deplored, the scientific microscopist being dependent 

 upon Continental workshops for that instrument of research 

 which is second only in importance to the microscope 

 itself. 



The Cambridge Rocking Microtome. — One instru- 

 ment of British manufacture and invention has won a 

 world-wide reputation : we refer to the Cambridge rocking 

 microtome, made by the Cambridge Scientific Instrument 

 Company. This is, however, a special microtome, inasmuch 

 as its mission is the cutting of small and soft objects em- 

 bedded in paraffin wax, for which exact purpose it has few 

 superiors. It is figured on p. 144. 



Good as is this microtome, it is not absolutely faultless, 

 although its failings have been magnified. Hard words 

 have been addressed to it, yet we think had the impreca- 

 tions been to the workers instead of to the microtome, there 

 would have been less perversion of truth and justice. 



A new ' rocker ' has recently been placed on the market 

 by the same makers, in which the faults which had 

 been alleged against the old pattern have been eliminated. 

 Eespecting the tenuity of the sections obtainable with this 

 microtome, it is probable that the instruments vary slightly. 

 The writer's is as follows : 



Forty-two turns of the micrometer screw will advance 

 the object -^V of 1 inch. 



One turn of the micrometer screw will advance the object 

 ^ir of 1 inch. 



As there are 224 teeth to the micrometer wheel, 1 tooth 

 of the same will advance the object jtIto of an inch. The 

 sector may be set to as many as 37 teeth of the wheel, 

 which is the maximum. The following table may be of 

 use : 



