CONTRIBUTIONS FROM THE ZOOLOGICAL LABORATORY OF THE 

 MUSEUM OF COMPARATIVE ZOOLOGY AT HARVARD COLLEGE. 

 E. L. MARK, DIRECTOR. — No. 187. 



AN ELECTRIC WAX-CUTTER FOR USE IN 

 RECONSTRUCTIONS. 



By E. L. Makk. 



Presented December 12, 1906. Received December 17, 1906. 



Any one ■who has had much experience in making models of micro- 

 scopic objects by means of wax reconstruction-plates must have felt 

 the disadvantages of the ordinary method of cutting out the plates with 

 a scalpel. 



Some years ago the advantages of heating the scalpel in a flame 

 suggested to me the desirability of employing a knife heated to a 

 constant temperature, and observation of the methods employed in 

 making corrections to " line process " plates prepared by the so-called 

 wax method led me to think it might be possible to use for this pur- 

 pose a small gas jet attached to the knife and connected with the gas 

 supply by a small flexible rubber tube. I did not succeed, however, in 

 producing a device that would work satisfactorily. A little later it 

 occurred to me that a wire heated by an electric current might be kept 

 at a sufficiently constant temperature to answer the purpose. Accord- 

 ingly in an ordinary bow-saw with large bow the saw blade was re- 

 placed by a fine wire, the ends of which were insulated from the frame 

 and connected by means of flexible insulating wire with a 110-volt 

 alternating electric circuit. By introducing into the circuit the proper 

 resistance — in the form of electric lamps arranged in multiple — it 

 was possible to heat to the proper degree the wire selected. By means 

 of this apparatus one could melt a wax plate readily along any pre- 

 determined course, provided the wire were slowly moved back and 

 forth as in sawing. But this apparatus was defective, owing to the 

 lengthening of the wire and its consequent laxness when heated. It 

 became obvious at once that for accurate work some sort of spring 

 would have to be introduced into the mechanism to take up the slack of 



