of Phosphorus in Animal and Vegetable Tissues. 469 1 



reducing reagent is allowed to act on a nitric acid solution of ammo- 

 nium molybdate, a brownish-black or black colour is produced, and an 

 amorphous precipitate may be formed, which, under the microscope 

 has a grey blue-black appearance, the fluid itself remaining brown,, 

 the colour being due to the oxidised pyrogallol. At the end of 

 twenty-four hours the amorphous elements are black, with or with- 

 out a brown shade. When, on the other hand, pyrogallol acts on 

 ammonium molybdate in solution the resulting colour is deep brown,, 

 very much like that of a saturated solution of Bismarck brown, 

 which is maintained at the end of twenty-four hours, but in no case 

 is a precipitate formed. It must be noted in this case that the colour 

 formed results immediately on the addition of the pyrogallol. 



That what happens in the test-tube is what also obtains in tissues 

 may be shown readily. If one impregnates sections of tissue with 

 ammonium molybdate for an hour or more, these, thoroughly washed 

 and then treated with a pyrogallol solution, give a brown colour,, 

 which is most marked in the parts of the cells which have an affinity 

 for colouring matters. It is obvious that in the absence of nitric acid 

 there is no phospho-molybdate compound present, and yet the reducing 

 reagent shows that though repeated washings were resorted to, the 

 ammonium molybdate has not been removed. On the other hand, 

 when the tissues are placed in a nitric acid solution of ammonium 

 molybdate the results obtained are strikingly different. One may 

 conveniently demonstrate these by placing fresh Spirogyra threads in 

 the solution for from five to ten hours at a temperature of 35 40 C.> 

 then washing them quickly in distilled water and putting them in a 

 freshly prepared strong aqueous solution of pyrogallol. In ten 

 minutes the threads may be again washed, dehydrated, cleared in oil 

 of cedar, and mounted in balsam. Wherever in such preparations 

 one expects to find phosphorus, e.g., in the nuclei, it is demonstrated 

 by the green reaction. If the pyrogallol is allowed to acfc longer 

 than ten minutes it begins to stain the cells and to mark the green 

 more or less with a brown coloration, which distributes itself in them 

 as colouring matters generally do. 



Perhaps the most striking way of demonstrating that the phospho- 

 molybdate is turned green and the molybdate brown by the action of 

 pyrogallol, is by impregnating portions of thin strips of writing paper 

 with a solution of sodic phosphate, drying them, and then submitting 

 them to the action of the nitric-molybdate solution, which gives them 

 a yellow colour. On now washing them in distilled water, and sub- 

 mitting them to the pyrogallol solution, the areas which are impreg- 

 nated with the phospho-molybdate become green in a few seconds, 

 while the parts which contain the molybdate solutioft alone become- 

 brown or yellowish -brown, and the contrast between the two reac- 

 tions thus appears marked. 



