1892.] MICROSCOPICAL JOURNAL. 289 



is complete and the sections adhere to the slide. The time re- 

 quired for this varies according to the thickness of the sections; 

 for thin sections one hour is generally sufficient for complete fixa- 

 tion, but the important point is that the paraffin must never be 

 melted until the last trace of water has disappeared from the 

 slide. If this premature melting happens by any accident, the sec- 

 itons are certain to peel oftlater. A few experiments enables one to 

 be sure of the point when the slides are safe. 



After complete fixation the paraffin is melted by putting the 

 slide inside the oven and then washed oft' with turpentine or 

 xylol. 



One of the great advantages of this method is the perfect ease 

 and safety with which it allows sections on the slide to be manipu- 

 lated, so that the most various stains and reagents can be applied 

 successively to a slide, e. g., the complicated processes used to 

 demonstrate bacteria in the tissues can be applied, with the cer- 

 tainty, moreover, that there is nothing on the slide to be stained 

 which was not in the section. — American Naturalist., Novem- 

 ber. i8g2. 



Geometrical Representation of the Formula for Lenses. 



— ]M. d'Ogagne states in Central-Ztg. f Optik u. Mechanik, xiii 

 (1S93), that by a well-known construction the magnitudes oc- 

 curring in the formula 



p"^p--f 

 may be represented by the distances in which a straight line 

 rotating about a fixed point cuts two rectangular axes, and the 

 distance of the centre of rotation from the centre of the co-ordi- 

 nates. He remarks that this construction is more convenient if 

 the axes are taken as intersecting at an angle of 120° instead of 



Apparatus for Cultivating Anaerobic Micro-organisms 

 on Solid Transparent Media. — Dr. A. Trambusti describes in 

 Centralbl. f Bakteriol. u. Parasitenk., xi (1S92), pp. 623-4, ^" 

 apparatus which he has devised for cultivating and examining 

 anzerobic microbes. 



It is made of glass and consists of two parts, the lower of which 

 resembles an inverted funnel, while the upper is cylindrical. In 

 the latter are two openings, the top one tightly closed with a 

 stopper, while that at the bottom is very small. Inside the cyl- 

 inder is a smaller one which is in communication with the funnel- 

 shaped clasp or lower portion of the apparatus. The apparatus 

 is used as follows: The medium, already inoculated, is spread 

 on the bottom of the flask and then this is closed by placing the 

 cylinder on it. Into the latter is then poured as much of the 

 ordinary pyrogallate of potash solution as may be necessary to 

 absorb all the air in the apparatus. The stopper having been put 

 in, the whole apparatus is placed in the thermostat. Two grm. 



