238 CHAPTER XVII. 



Molybdate of ammonium . . 1 grm. 



Distilled water . . . .10 grms. 



Peroxide of hydrogen ... 1 grm. 



On adding the peroxide a yellow colour is produced. A 

 drop of hydrochloric acid is added (white precipitate of 

 molybdic acid which dissolves on agitation). After staining 

 and rinsing in salt solution the preparations are put into the 

 molybdic solution. The solution ought not to be more than 

 eight days old, and it is well to use it cooled to zero. The 

 preparations are left in it for two or three hours if they are 

 small, or four or five hours if they are large (of a centimetre 

 in size) . They are then washed for from half an hour to two 

 hours in water, dehydrated in alcohol (which it is well to use 

 cooled to zero), and cleared in clove oil,, or, better, in xylol. 

 They may then be imbedded either in paraffin or celloidin in 

 the usual way. 



This is for tissues of Vertebrates. For Invertebrates 

 BETHE takes one grm. of molybdate, 10 c.c. of water, and 0'5 

 <?.c. of peroxide. 



PEABODY (Zool. Bull, i, 1897, p. 163; Zeit.f. iviss. Mile., xvi, 1, 1899, 

 p. 73) adds a drop of 1 per cent, osinic acid. 



ETHK'S later method (Anat. Ariz., xii, 1896, p. 438) is as 

 follows : After staining, pieces of tissue of 2 to 3 mm. thick- 

 ness are treated for ten to fifteen minutes with a concentrated 

 aqueous solution of picrate of ammonia and are then brought 

 into a solution of 1 grm. of molybdate of ammonium, either 

 in 20 of water, or in 10 of water and 10 of 0*5 per cent, 

 osmic acid or 2 per cent, chromic acid ; or into a solution of 

 phosphomolybdate of sodium in the same proportions, each 

 of these solutions having added to it 1 drop of hydrochloric 

 acid, and if desired 1 grm. of peroxide of hydrogen. They 

 remain in one of these solutions for three quarters to one hour 

 (or from four hours to twelve in the osmic acid one), and are 

 then passed through water, alcohol, xylol, balsam, or paraffin. 

 (The objects that have been treated with one of the solutions 

 of the sodium salt are not thoroughly resistent to alcohol, so 

 that for them it is well to cool the alcohol to under 15 C.) 

 Sections may be after-stained with alum carmine, or 

 " neutral " tar colours. 



Slight modifications of this method are given by DOGIEL 



