THE BACTERIOLOGICAL LABORATORY 29 



tions of diseased organs, etc. Dr. Sims Woodhead 

 has somewhat modified the Cambridge rocking 

 microtome by adding a solid end to the brass tube 

 into which ' dies ' of various sizes, with roughened 

 surfaces, can be screwed. ' This does away with the 

 inconvenience of having to " melt in " the imbedded 

 tissue into the tube. A dozen of the dies may 

 be used, and to each of these a piece of tissue 

 may be fused, and kept ready for cutting at any 

 time. ' 



Besides the microtomes just mentioned there are 

 those of Korting, Eeichert, and Jung, which are 

 principally used in France and Germany. When 

 tissues are to be examined in the fresh state, 

 either Koy's or Williams' freezing microtome should 

 be used for section-cutting. In the former instru- 

 ment the tissue is frozen by means of an ether 

 spray ; while in the latter the frozen tissue is pro- 

 duced by a mixture of ice and salt. There is no 

 doubt that Eoy's microtome is the better instrument 

 of the two, as the freezing of the tissue only 

 occupies from thirty to forty seconds ; and this 

 microtome may also be used for cutting objects 

 imbedded in paraffin and not requiring freezing 

 in other words, the instrument can be used both 

 as a freezing and a non-freezing microtome. 



Tissues imbedded in paraffin or a mixture of 

 white wax and olive oil may be cut by hand with 

 a hollow-ground razor. The razor is dipped in 

 dilute alcohol and then drawn diagonally across the 

 mass (containing the specimen) with a steady 

 sweep. Before cutting each section the razor 



