274 The Mickoscope. 



regularly until the whole is thoroughly mixed ; strain through a 

 piece of close, clean iiannel into a flask, in which it may be 

 re-heated over the water-bath as required. When not in use the 

 flask should be kept well corked. Having allowed most of the water 

 to drain away from the section by filtering, with the glass protecting 

 the section from dust (it must not be allowed to dry or air bubbles 

 will be enclosed in the section and it will be spoiled), it is placed, 

 section upwards, on a level stand (a screw tripod serves the purpose 

 admirably), and a thin layer of the warm glycerine jelly is run 

 gently over the surface of the section by means of a pipette. Great 

 care must be taken not to allow the jelly to run too rapidly, or the 

 margins, or even the whole section, may be displaced. It is then set 

 aside to cool, after which, if kept away from dust and heat, it may be 

 left for a week or two until time and effort be found to finish it off. 

 This finishing-off process requires a little practice, but it is not 

 difl&cult. The slide on which the section is to be mounted is placed 

 on three or four pieces of cork over a water-bath until it is warmed 

 through. This is to prevent the too rapid setting of the jelly. It 

 is then transferred to the tripod, and a quantity of jelly is poured 

 onto the center and gradually onto the end nearer the manipulator. 

 The cover-glass is then taken and gently lowered, the near end first, 

 and so gradually down onto slide. 



The jelly on the cover keeps the section in position sufficiently 

 long to allow of the cover-glass coming into its place. The slide 

 usually retains sufficient heat to melt away all superfluous jelly. 

 Should this not be the case, the whole slide may be again heated over 

 the water-bath, and by the application of gentle pressure, the extra 

 mounting medium is squeezed out. If this surplus medium be left 

 at the margin of the cover, the slide may be left for some time with- 

 out further treatment. To preserve the specimen, remove the extra 

 jelly with a spatula or knife, wipe carefully, first with a moist, then 

 with a dry cloth. Then paint the margin of the cover- glass and the 

 slide with benzol balsam, layer after layer being applied at intervals 

 of two or three days, until there is a good firm coating. Unless 

 this be done at once after clearing off the extra jelly, the jelly at the 

 margin under the cover dries rapidly, air-bubbles getting under the 

 cover and spoiling the section. I have found that it is good to 

 mount these in common wooden frames like slate frames, so that the 

 cement may be examined from time to time, and, if necessary, 

 repaired. The sections are now ready for examination. Specimens 

 of normal lung, (1) uninjected; (2) injected with carmine gelatin; (3) 

 sections of emphysematous lung uninjected: (4) injected with Prus- 



