884 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and then carefully washed again and mounted (a) simply in glycerine, 

 or (b) in dammar, after staining with saffranin. 



The delicacy of the sections necessitates the employment of good 

 daylight, and illumination from below in their manipulation ; the 

 latter end may be attained by employing as working stage a cigar 

 box, from which the front side has been removed, putting a piece of 

 glass on the top, and an oblique mirror inside. Great care must be 

 taken not to allow contact between the sections when made, as they 

 would then probably become entangled. 



TJnpressed Mounting.* — Under this heading Mr. A. W. Stokes 

 describes the mounting of the tongue of a blow-fly " without pres- 

 sure," so that its true shape is preserved, a halfpenny test-tube being 

 all the preparing apparatus required. 



Into this test-tube place the fly's head, and fill the tube half-full 

 with a solution of soda and potash. Staud the tube in boiling water, 

 and leave it on the hob of a fire to keep hot till morning. Then 

 examine the head and see if it looks almost transparent ; if not, pour 

 off the soda solution and add a fresh supply, and again keep the 

 tube hot till the object becomes semi-transparent. Now pour off the 

 solution and add hot water, in a few minutes emptying it out and 

 adding some more: — Kepeat this at least three times, and finally 

 leave the last quantity of water on the object for an hour to cool. 

 Next pour off all the water and replace it with spirit of wine ; 

 methylated spirit, if strong, will do sufficiently well. Heat this by 

 immersing the tube in a vessel of hot water for one minute; then 

 take it out, cork it up, and leave it for one hour. 



So far we have, by means of the soda-solution, destroyed all the 

 flesh and fat tissues, leaving only the cuticle and internal organs, such 

 as the tracheae, &c. In doing this, we have filled up most of the few 

 natural air-spaces with soda-solution, which, however, being a some- 

 what dense fluid, would not enter many of the narrow tracheal tubes. 

 Then with water we replaced the soda-solution, and washed away the 

 parts destroyed thereby. On replacing the water by alcohol, a still 

 less dense fluid, more of the finer air-spaces are penetrated and the 

 air driven out ; there are still, however, some tubes too minute even 

 for alcohol rapidly to enter. So now we pour off the spirit, and 

 add ether instead, which answers a double purpose ; it enters the very 

 minutest passages, displacing the contained air, and it also dissolves 

 the globules of fat left unsaponified by the soda-solution. After 

 leaving the ether for fifteen minutes in the corked tube, and shaking 

 it once or twice, we pour it off and add turpentine ; and then in ten 

 minutes time the head is ready for mounting in Canada balsam or 

 dammar. 



If so mounted, however, it will be very difficult to see much of 

 the finer internal structure, since these media render some parts far 

 too transparent ; and hence some of the glycerine media are pre- 

 ferable. In such cases, after pouring off the ether, add alcohol, and 

 at the end of fifteen minutes replace the alcohol with cold water, and 



* Journ. Post. Micr. Soc., i. (1882) pp. 129-35. 



