1894.] MICROSCOPICAL JOURNAL. 131 



should not be added until immediately before use, for, 

 if allowed to remain too long, it is liable to crack and 

 fall away. Tlie slip of glass thus prepared with the 

 strip of paper covered with its two films of gum and col- 

 lodion is then ready for use. 



The object to be oriented, which has been previously 

 cleared in turpentine, is now drained of the superfluous 

 oil by means of bibulous paper, and brought on the point 

 of a needle to the surface of the paper prepared as above, 

 and adjusted under the microscope so that the axes of 

 the object have any desired relation to the lines on the 

 paper. If care be taken to drain off all of the turpen- 

 tine from the object, it will stick to the surface of the 

 collodion in any position in which it is placed, so that an 

 oblong or ovoid object can be placed either on end, or so 

 that its chief axis will make almost any angle with the 

 plane of the paper. When the object is suitably oriented, 

 the whole slide is exposed under a bell glass for a few^ 

 seconds to the vapor of ether. This softens the collodion, 

 which upon drying holds the object fast in the desired 

 position. The object is then covered with a drop of tur- 

 pentine, and the slip of glass with the attached paper is 

 placed in the paraffin bath. 



To imbed the object in paraffin, the slip of glass bear- 

 ing the object is removed from the bath, and a mould is 

 built upon it about the paper in the ordinary way, by 

 means of bars of metal arranged in the form of a rec- 

 tangle, and filled with fluid paraffin. The mould should 

 be as nearly as possible of the same size as the strip of 

 paper, that is to say, the sides of the mould should coin- 

 cide with the edges of the paper. When the paraffin has 

 cooled, the metal guards are carefully removed, and the 

 paraffin is cut away until the edges of the paper are ex- 

 posed. This is an important preparation for the next 

 step. The glass slip with the attached block of paraffin 

 is then put into a vessel of water. The water working 



