52 R. K. BENSLEY. 



are first affected, then lecithins, and finally the organic compounds 

 of phosphorus. Where it is desired to demonstrate the distribu- 

 tion of the latter he recommends the preliminary removal of the 

 lecithins by repeated extraction with hot ethyl alcohol in a 

 Soxhlet apparatus. 



In the original form devised by Lilienfeld and Monti or in the 

 form of Macallum's modification this reaction for phosphorus has 

 been extensively employed. Macallum's original paper dealing 

 with the reaction contains a considerable number of contributions 

 dealing with the distribution of organic compounds of phosphorus 

 in various tissues, and the reaction has been applied to the solu 

 tion of special problems of this nature by Sherrington ('94), 

 Gourlay ('94), Scott ('99), Held ('95), Bensley ('03), Wager 

 ('05), Richter ('05), and many others. It is therefore of the 

 utmost importance that every detail of the reaction should be 

 carefully tested to exclude all possible sources of error. 



Recently I have obtained results which have led me to suspect 

 that the reaction obtained by Macallum's method is not wholly 

 due to the formation in the tissue of ammonium phosphomolyb- 

 date, but that other compounds of molybdenum may be present 

 which are capable of reduction to the blue oxide by means of 

 phenylhydrazin hydrochloride. For example, I observed that 

 the peripheral portions of sections gave uniformly a deeper and 

 more diffuse reaction than the central portions. This result was 

 first noted in the tips of the villi in sections of the small intestine, 

 and was ascribed to the presence of inorganic phosphates ab- 

 sorbed from the food. Later it was noted that the same result 

 was obtained in sections of the liver, pancreas, and other organs. 

 Furthermore, I observed that freshly prepared solutions of the 

 nitric molybdate often gave a strong reaction in the tissues after 

 very short periods of immersion. For example, sections of the 

 fundus region of the stomach of the rabbit, treated with warm, 

 freshly prepared nitric molybdate reagent for ten minutes, then 

 washed in water and reduced by means of a one per cent, solu- 

 tion of phenylhydrazin hydrochloride gave a diffuse bluish green 

 reaction together with a strong reaction in the nuclei and in the 

 granules of the parietal cells. This result was clearly not due to 

 phosphorus compounds of any sort, because the same nitric 



