The Microscope. 21'6 



•cat's-lung about one-half inch long, three-eighth inch wide and one- 

 ■quarter inch thick, with a portion of the capsule running lengthwise, 

 and drain off the superfluous alcohol by means of a blotter. By this 

 time a film sufficiently strong to just bear the weight of the specimen 

 will have formed on the surface of the mass in the box. With a pair 

 •of forceps grasp the specimen and carefully place it lengthwise on 

 this film with the end fi'om which the sections are to be made about 

 three-eighth inch from the end of the box. Now from the pipette 

 slowly run in sufficient of the mass to fill the box. This mass should 

 be hot enough to melt the surface of the film ; yet, on the other 

 hand, not so hot as to dissolve it altogether, thus allowing the 

 •object to fall to the bottom. With a little practice this can be easily 

 performed. When the mass has hardened thoroughly, it can be re- 

 moved from the box and is ready for immediate work, or it can be 

 labeled and laid away for use in the future. 



For cutting, see that the section knife or razor is in good condi- 

 tion. Fill two dishes each with stronger alcohol. With a pocket- 

 knife carefully pare away the superfluous paraffin from the edges and 

 end of the block. In doing this, care should be taken not to expose 

 the specimen, for the dull blade will catch and disarrange it. Now 

 rest the lower end of the block on the table and grasp firmly with 

 one hand. Di]^ the knife in the alcohol so that the upper concave 

 surface will be filled with it. [Note : In cutting, keep this concavity 

 CONTINUALLY filled, for if the blade become even partially dry it will 

 almost certainly tear the specimen.] Now cut successive thin sec- 

 tions from the paraffin-cover, and keep on till the specimen is reached 

 and a sufficient number of sections are obtained from it. The knife 

 must be managed in the following manner : Begin at the heel of the 

 blade and cut by drawing through the specimen. Do not push the 

 blade into the object nor saw it to and fro. Make the section with 

 one slow sweep so that when separated it will glide on to the blade 

 near the tip. It can then be floated off into the extra dish with a 

 gentle urging_from a camel's hair brush. 



If it is desired to cut more sections from this specimen at another 

 iime, the block must now be put in alcohol, as the uncovered object 

 Avould otherwise shrivel and become useless. 



The specimen is now to be treated as follows : Handling it by 

 Tise of paraffin, or tissue-paper, as described in the last lesson (page 

 174,) it is to be removed from the stronger alcohol and exposed for 

 a few minutes until comparatively dry. Place it in a liberal quanti- 

 ty of xylol and leave for about an hour. This is for the purpose of 



