S. S. mouse 



PARAFFIN SECTIONS 



141 



out at the same time tliat tlic skin of the 

 tail is being cut. Remember that after fine 

 adjustment, the knife blade will have to 

 be used as a plane to render flat the whole 

 surface of the block before further com- 

 plete sections can be taken. Finally, how- 

 ever, the moment comes which culminates 

 all the months of work. The block is lying 

 completely flat. One places a freshlj^ sharp- 

 ened knife in position and prepares to take 

 the sections required. 



Before this final operation it will be nec- 

 essary to have cleaned, in any manner de- 

 sirable, the required number of slides, and 

 to have laid these at hand alongside the 

 vessel of water which will be used for flat- 

 tening. Now take the brush in the left 

 hand, the knife in the right hand, shde the 

 knife forward, grab the little curling tail 

 of paraffin coming from the pointed end 

 of the block, and with one smooth, con- 

 tinuous movement complete the section. 

 This section, in a more or less wrinkled 

 condition, will now be l3'ing on the knife 

 blade, from which it may be removed with 

 the aid of two brushes. One l:)rush held in 

 the left hand is moistened with the lips 

 and applied to the upper surface of the 

 end of the section farthest from the edge 

 of the blade, while the other is very gently 

 slid under the section to loosen its attach- 

 ment from the edge of the blade. Using one 

 brush b}^ adhesion from above and one 

 brush to balance the other end of the sec- 

 tion from below, now drop the section onto 

 ' the warm water where it will completely 

 expand. A slide is then taken in the right 

 hand and a needle in the left, with a view 

 to stranding the section in the right posi- 

 tion on the shde. 



The slide should be placed in the water 

 and left for a moment or two until it 

 reaches approximately the same tempera- 

 ture and then, while held pointing down- 

 wards at an angle of about 45°, ap- 

 proached to the section until that side of 

 the section which is intended to be to- 

 wards the upper end of the slide just 

 touches the glass. The slide is tlien very 

 shghtly raised so as to strand the ui)per 

 portion, which is then held in place with a 

 needle while the whole shde is withdrawn 

 at an angle of from 45 to 30° from the 

 water. It is quite impossible to pass the 

 slide horizontally under the section and 



then to I'aise it so that the section remains 

 in place. It is only by withdrawing the 

 shde at an angle, in the manner described, 

 that one can hope to strand the section in 

 the correct position. If tlie section is not 

 ill correc't position on tiie slide, no attempt 

 can be made to rearrange it. It is only pos- 

 sible to replace the slide in water with the 

 hope that the section will float off so that 

 a second attempt can be made. If the sec- 

 tion is only slightly out of position on the 

 slide it is much better to leave it alone, 

 since the section usually breaks at the sec- 

 ond attempt to strand it. As soon as the 

 section has been stranded on the slide, the 

 slide is removed from water, laid on a flat 

 surface, a sheet of water-saturated coarse 

 filter paper laid on top of it, and a rubber 

 roller of the type used by photograjjhers 

 pressed down with considerable force so 

 as to squeeze the water from the paper 

 and the section at the same time. The 

 section is then placed on a warm table to 

 dry. 



Notliing has been said about the use of 

 an adhesive for attaching the section to 

 the shde. Provided that the slide is per- 

 fectly clean and that the section is pressed 

 firmly into contact with it, there should 

 be no necessity for any adhesive at all. 

 For those, however, who do not care to 

 run this risk any adhesive mentioned in 

 Chapter 2S under tlie heading of V 21.1 

 may be used either by smearing it on the 

 slide, or mixed, to the extent of about 2%, 

 in the water used for flattening. 



As soon as the slides are dried they may 

 be stained in any manner desired. For a 

 specimen of this nature the wn-iter's first 

 ])reference is for the stain for Patay 1934 

 (ab])reviated directions for wiiich will be 

 found in Chai)ter 20 under the heading 

 DS 12.32 Patay 1934) or for the stain of 

 Mallory (which will be found in the same 

 chapter under the heading DS 13.41). De- 

 tailed descriptions of the use of both of 

 these stains are given elsewhere. 



If 'the slides have to be stored for any 

 great length of time, or if the process of 

 decalcification has been unduly prolonged, 

 treat each shde before staining according 

 to the method of Mullen and McCarter, 

 which is given in Chapter 22 under the 

 heading ADS 12.1 Mullen and McCarter 

 1941. 



