982 SUMMARY OF CURRENT RESEARCHES RELATING TO- 



The plane thus altered works upon two strips of plate glass, which 

 can be adjusted to the width of the iron, and easily renewed if broken, 

 being kept in position by wooden bars which act as guides to the plane. 



The inside edges of the guides just allow the plane to work freely 

 upon the glass, and the edges of the glass are adjusted carefully so as 

 to allow the plane-iron to pass between without touching them. 



The top of the table is roughened with a file, and not grooved, in 

 order to secure more evenly and firmly the substance to be cut, and 

 in the spray small brass nozzles are used which can be renewed 

 when desired. 



In use, the whole instrument is clamped to the left-hand corner 

 of a table, with the side towards the operator. The cutting edge of 

 the plane-iron being fixed about 3/16 in. above the top of the table, 

 and the substance to be cut being frozen, the operator firmly grasps 

 the plane with his right hand, and causes it to travel backwards and 

 forwards between the guides, while he leans over the instrument, and 

 with his left hand, before each cut, turns the large screw-head 

 through one or more divisions, according to the thickness of the 

 section desired. In turning the screw-head, the worker will be 

 guided by the nick in the little brass screw in the end of the wooden 

 base of the instrument. 



Any advantages of a diagonal cut may be secured by placing the 

 substance to be operated upon in a diagonal position upon the table. 



Preparing Pier o carmine and Indigo-Carmine.* — Dr. F. L. James 

 writes that whilst picrocarmine is one of the most valuable staining 

 agents, the formula for preparing it, " for some unaccountable reason, 

 is not given in any of the standard works on the subject, and micro- 

 scopists are forced to purchase it from dealers at exorbitant prices," 

 and he therefore gives the following as the process used in his 

 laboratory for preparing a very satisfactory article. 



" Dissolve 15 grains of the best carmine in the smallest quantity 

 possible of strong water of ammonia, and add distilled water enough 

 to make one ounce of the solution. In a separate vessel dissolve 75 

 grains of picric acid in the smallest amount of boiling distilled water, 

 making a saturated solution. When cold pour the two solutions 

 together, and let stand in a closely stoppered bottle for several days, 

 giving it an occasional shake. At the expiration of four or five days 

 ■ filter the solution, and pour the filtrate into flat dishes ; saucers or 

 soup-plates will do. Cover with a plate of glass close enough to keep 

 out dust, but not so closely as to prevent evaporation. Put in a 

 moderately warm place, and let stand until the fluid has entirely 

 evaporated, leaving a crop of fine brickdust-red crystals. These 

 should be collected, thoroughly dried, and preserved. When required 

 for use, dissolve in about fifty times their weight of distilled water, 

 filter the solution, and keep in glass-stoppered vials. Do not make 

 more than an ounce of the solution at once, as a little of it goes a long 

 way." 



* Amer. Mon. Micr. Journ., v. (1884) pp. 178-9 and 199, from 'National 

 Drugaist.' 



