SECTION CUTTING. 



189 



in a thick and syrupy solution of gum arabic ; if time is 

 no object it is a great advantage to soak them in this 

 for several hours. A block is then placed on the 

 corrugated plate of the microtome and frozen by means 

 of the ether spray which impinges upon it. When the 



FIG. 31. Cathcart's microtome arranged for cutting frozen sections. 



mass is nearly frozen a section is taken off by means of 

 a razor which is ground flat on one side, or the special 

 knife which may be obtained with the apparatus : it is 

 better to moisten the upper surface of the knife with a 



