62 R. R. BENSLEY. 



tion which was due to ammonium molybdateand to molybdic acid, 

 and that a considerable residuum of the reaction would be found 

 unaffected by even high concentrations of nitric acid and could 

 thus be interpreted as a true phosphorus reaction. I was quite un- 

 prepared for, and greatly disappointed at the actual result of these 

 experiments, namely, that relatively low concentrations of nitric 

 acid abolished the reaction altogether. 



With a concentration of 3.27 per cent, of nitric acid, phenyl- 

 hydrazin hydrochloride o.i per cent., the molybdic acid sections 

 and the nitric molybdate section showed no reaction after three 

 minutes' treatment, although the section containing ammonium 

 phosphornolybdate artificially introduced gave a maximum reac- 

 tion in less than one minute. After fifteen minutes' action, a 

 very faint reaction was obtained in the nuclei, both in the mo- 

 lybdic acid section and in the nitric molybdate section. When 

 the concentration of the nitric acid reached 16.37 P er cent., the 

 phenylhydrazin remaining the same, the reaction was not recog- 

 nizable after fifteen minutes' treatment although sections contain- 

 ing ammonium phosphomolybdate artificially introduced reduced 

 to a maximum depth of color in the same solution in five minutes. 

 I have repeated these experiments many times, always with the 

 same results. It is significant that the reaction disappeared at 

 exactly the same point as regards concentration of nitric acid in 

 the molybdic acid section and the nitric molybdate section. 



Only one conclusion is possible from these experiments, 

 namely, that sections after treatment with Macallum's reagent 

 for this length of time did not contain appreciable quantities of 

 ammonium phosphomolybdate. Thus the fundamental assump- 

 tion on which the reaction of Lilienfeld and Monti and of Macal- 

 lum is based falls to the ground. It is obvious that if the phos- 

 phorus of the organic compounds is liberated at a point short of 

 the destruction of the recognizable structures of the cell, it is not, 

 at all events, precipitated in situ by the nitric molybdate reagent. 



As a result of these experiments I am of the opinion that the 

 reaction obtained by Macallum's procedure is entirely due to the 

 formation of compounds of molybdic acid with the albumens of 

 the tissue and not in any respect to the formation of ammonium 

 phosphomolybdate at the expense of the organic phosphorus. 



