228 Specific Examples of Slide Making 



removed, t here will be crystallization with consequent damage to the 

 tissues. 



Small pieces may now be removed for embedding from the testis itself. 

 It is best to select pieces about 1 mm in from the surface and from a side 

 of about 2 mm. These should be embedded in paraffin and cut about 5 fx, 

 thick in the usual manner. Then the sections should be attached to slides, 

 particular attention being paid to the fact that the slides are clean and that 

 not too much Mayer's albumen, which may interfere with differentiation 

 or staining, is used. 



The dry sections attached to the slides should be warmed on the under- 

 side until the paraffin melts, placed in xylene until the paraffin is removed 

 completely, and then run down in the ordinary way through absolute 

 alcohol and lower percentage alcohols to distilled water. Then they should 

 be lifted from the distilled water and examined carefully. If there is a 

 tendency for the water to gather in droplets on the slide or, if upon shak- 

 ing the water from the slide, each section appears to retain an adherent 

 coat of water around itself, it is an indication that either the wax was not 

 removed properly in the xylene or that the xylene itself is so old as to 

 have a wax content too high to be useful. Such slides must be returned 

 through the alcohols to absolute alcohol and thence to clean xylene where 

 they should be left for a few minutes before again being brought down 

 to the water and reexamined. There is no more common cause of the fail- 

 ure of the stains to take than the imperfect removal of the wax . 



Only two solutions are required for staining. These are a 2.5 per cent 

 solution of ferric alum and a 0.5 per cent solution of hematoxylin. The 

 only difficulty in making the ferric alum solution is to obtain a pure and 

 unoxidized sample of the reagent. Most of the crystals in a new bottle are 

 of a clear violet color, but after a bottle has been opened for some time, 

 particularly if the stopper is loose, most of the crystals become covered 

 with a brownish deposit that must be scraped off with a knife before the 

 solution is prepared for staining. If the brown powder on the outside of 

 the crystal forms a layer of any thickness, it is best to reject the whole 

 and get a fresh supply of the reagent. Hematoxylin itself has little stain- 

 ing effect; the color is produced by the formation of lakes with hematein, 

 an oxidation product of the hematoxylin. It was customary in former 

 times to prepare large quantities of solution, which were kept with the 

 stopper loose in the bottle for a period of at least one month before use. 

 For the purpose of Heidenhain's technique, however, i t is far more im- 

 portant that a small quantity of the ferric alum should be carried over into 

 the hematoxylin solution than that the latter should be aged . The staining 

 will be found both simpler and more effective if a few drops of hema- 

 toxylin are placed in the iron alum solution and a few drops of the iron 

 alum solution are placed in the hematoxylin. Both solutions, of course, 



