APP.] CUTTING SECTIONS. 435 



raised through a hole in a glass plate, across 

 which a razor held in the hand is pushed. We 

 will briefly describe the method of manipulation 

 for the small microtome, it will be found easily 

 applicable to Jung's sliding microtome. 



The paraffin block is pared in such a manner 

 that the edge nearest to the operator and that 

 opposite to him are parallel. A dry razor is 

 then pushed upon the glass plate over the hole 

 through which the block of paraffin projects up- 

 wards, and a section cut which remains upon 

 the razor. Care must be taken that the edge of 

 the razor is parallel to the parallel edges of the 

 l)araffin block. The block having been raised 

 bv the screw, a second section is made in the 

 same way and on tlie same part of the razor as 

 the first ; in consequence of which, the first 

 section will be pushed backwards by the second. 

 Similarly each new section pushes backwards 

 those already made ; and a ribbon of sections 

 formed which, if the paraffin is of the right 

 consistency, will adhere firmly together. 



Experience must teach the manipulator how 

 to mix the paraffin in such a manner that it is 

 neither too hard nor too soft ; if it is too hard, 

 the sections will not adhere together and will 

 curl up on the razor, if too soft they will 

 stick to the razor and be found to be creased. 

 When it is not possible to keep the temperature 

 of the room constant it will be found convenient 

 to use a hard paraffin, and when necessary to 

 raise the temperature by means of a lamp. 



The paraffin should completely surround the 

 embryo and fill up all the spaces within it. 



282 



