ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 707 



half an hour; for larger objects a correspondingly longer time is 

 required. The preparations thus soaked in paraffin are next allowed 

 to set on a glass plate. The sections are fixed in the usual manner 

 by the shellac solution, and this having been done the paraffin is dis- 

 solved out in benzol. When it is certain that all the paraffin has 

 disappeared, Canada balsam dissolved in benzol may at once be 

 dropped on and the cover-glass put in place. 



When dealing with delicate sections or with fragile and easily 

 lacerable tissues, all disposition to tear or break up may be avoided by 

 brushing over the upper surface of every section, as soon as it is cut, 

 a thin layer of collodion. By this means the preparation is covered 

 and held together by an adhesive and continuous coat. The collo- 

 dionized surface is that which is applied to the slide. The othear 

 steps of the process are, of course, the same as before. 



It may be noticed that all the author's specimens were treated with 

 a 5 per cent, solution of sublimate heated to 60°-70° ; pieces the size 

 of a pea are to be left in for 10 minutes ; those the size of a walnut for 

 half an hour. Thus hardened, the specimens are transferred directly 

 to 70 to 80 per cent, alcohol for at least 12 hours, and afterwards to 

 90 per cent, alcohol until all traces of the sublimate have disappeared. 

 The complete extraction of the sublimate may be known by evapo- 

 rating a drop or two of the last spirit in a watch-glass, in order to 

 ascertain if any acicular crystals of sublimate be deposited. 



The author recommends carmine for staining purposes, and the 

 fluid he employs is made as follows : — To a large teaspoonful of 

 carmine are added 500 grammes 70 per cent, alcohol, and to every 

 100 grammes of the foregoing 15 grammes pure hydrochloric acid. 

 The mixture is then boiled for some time in a water bath. After 

 boiling there should be a residue of carmine ; if not, add more carmine 

 and boil again. The spirit lost by evaporation is to be replaced by 

 96 per cent, alcohol. The fluid, having been filtered, is ready for 

 use. Preparations may be stained in bulk, and overstaining removed 

 by the use of 70 per cent, alcohol. 



By the foregoing method the complicated karyokinetic figures and 

 every intracellular detail can be demonstrated in the clearest manner. 



Sections of Teeth.* — Dr. W. C. Brittan finds that very beautiful 

 sections of the jaws of small animals with the teeth in situ may be 

 made in the following way : — 



The jaws of a well injected animal are placed for a few days in 

 50 per cent, alcohol, then into absolute alcohol for about two weeks, 

 then with a fine sharp filo cut away the bone from both sides of the 

 jaw where the section is desired until, by holding to the light, 

 the pulps of the teeth are visible, carefully keeping the piece and the 

 file wet with alcohol during the operation. Thoroughly wash the piece 

 with a soft brush in alcohol and place in clove oil for a few hours, 

 or until clear. Then transfer to a very thin solution of balsam in 

 benzole, gradually thickening the solution from day to day by adding 

 pure balsam until the tissues are thoroughly permeated. This is an 



* The Microscope, vi. ( 1 880) pp. 128-0. 



3 a 2 



