56 R. R. BENSLKY. 



and a deep blue in the collagenic fibers. Except for the strong 

 reaction in the connective tissue, the result obtained by treatment 

 of sections with a solution of molybdic acid containing nitric acid, 

 followed by reduction in one per cent, phenylhydrazin hydro- 

 chloride was exactly similar to the so-called phosphorus reaction 

 obtained by the procedure recommended by Macallum. It may 

 be noted that the color obtained by the use of molybdic acid con- 

 taining nitric acid followed by reduction differed from that pro- 

 duced by reduction of molybdic acid by phenylhydrazin in the 

 test tube, inasmuch as the former gives a greenish blue color, the 

 latter a pure blue. This difference was obviously due to the 

 yellow background afforded by the xanthoproteic reaction. As 

 in the phosphorus reaction, the absorption of the molybdic acid 

 was progressive, the reaction after eighteen hours being much 

 stronger than after three hours. 



Similar results were obtained with solutions of molybdic acid 

 containing hydrochloric acid, except that the molybdic acid was 

 taken up much more rapidly from the hydrochloric solution than 

 from the nitric solution, and that the resulting reaction was blue 

 rather than greenish blue, owing to the absence of the yellow 

 zanthoproteic reaction. A further difference exhibited itself in 

 the fact that sections left for some time in the solutions developed 

 the blue color witJiout the use of any reducing' agent, the organic 

 compounds of the tissue evidently acting as reducers. In the 

 presence of nitric acid this, of course, could not occur because of 

 the strong oxidative action of this compound. 



Thus, in sections treated with solutions of molybdic acid con- 

 taining either hydrochloric, or nitric acid, followed by phenyl- 

 hydrazin hydrochloride, results were obtained which were the 

 exact counterpart of the results of the so-called phosphorus 

 reaction, although there could be little possibility of the form- 

 ation of precipitates of ammonium phosphomolybdate in the 

 tissues. Curiously enough, the anomalous characters occasion- 

 ally observed in the reaction obtained by Macallum's method 

 wene to be found in the molybdic acid material, that is to say, 

 the more intense diffuse reaction of the outer portions of the sec- 

 tions and the deep reaction in the connective tissue. It seemed 

 clear from these experiments that a portion, at least, of the result 



