31 



blade is used in cutting the section. Recall that in the paraffin 

 method the knife is usually to be set at right angles to the direction of 

 the cut, and the stroke is a rapid straight one. Trim away the sur- 

 rounding celloidin mass leaving enough, however, to serve as a support 

 to the tissue and prevent its bending under the impact of the knife ; if 

 the celloidin mass is too tapering, bending will occur and thin sections 

 cannot be cut. To avoid this the celloidin block is best trimmed in 

 the form of a four sided truncated pyramid with as broad a base as 

 possible. 



Clamp in the jaws of the microtome, placing it so that the mass 

 of celloidin is opposite the side to which the pressure of the knife is 

 applied in cutting. It is advantageous also to have the object placed 

 with its long diameter parallel with the edge of the knife. 



When knife and tissue are properly arranged wet the tissue 

 well with clarifier or alcohol, as the case may be, and flood the 

 knife with the same. Make the sections with a slow, steady, motion 

 of the knife. With a small object (3x5 mm.) and a good sharp 

 knife, sections 5^ to 6^ can be cut without difficulty. In addition to 

 a sharp knife, however, there are necessary well-infiltrated tissue 

 and a hard, firm mass. If serial sections are not desired, it may be 

 more expeditious to cut dry and with a rapid stroke. 



70. Transferring the sections. If the sections are quite 

 thick they may be transferred from the knife to a slide or a dish by 

 means of forceps or a brush; if they are thin, however, it is better 

 to handle them by means of an absorbent tissue paper, as follows: 

 Flood the sections well with clarifier and then by means of a pipette 

 remove the clarifier from the knife and place over the sections the 

 end of a piece of the tissue paper, pressing it down upon the sec- 

 tions if necessa^. Carefully pull the paper off the edge of the 

 knife; the sections will adhere to the paper. Place the paper, sec- 

 tions down, on a slide, taking care that the sections are in the de- 

 sired position. With the finger carefully press the sections (through 

 the transfer paper) to the slide, and then lift the paper, with a roll- 

 ing motion, from the slide; the sections will adhere to the slide. 

 Should they stick to the paper instead, lower the paper again and 

 again firmly press the section to the slide. For further procedure 

 see 135, 136. If it is not desired to mount the sections upon a 

 slide immediately, or if they are to be kept in bulk, as for class 

 work, the transfer paper may be shaken gently in a dish of clarifier 



